Bug 656197 - Push state updates further out across beforesetattr/aftersetattr

* Remove the generic attr preparsing mechanism from BeforeSetAttr and just preparse class attributes directly in the one place that needs to do it
* Move calls to BeforeSetAttr to after AttributeWillChange
* Remove UpdateState calls in BeforeSetAttr
* Move calls to AfterSetAttr to before UpdateState when manipulating attributes
* Remove UpdateState calls from AfterSetAttr, since they are no longer needed there

Tag #1375

27 files changed, 84 insertions, 117 deletions

diff --git a/dom/base/Element.cpp b/dom/base/Element.cpp
index 91a3b63d75..055746885b 100644
--- a/dom/base/Element.cpp
+++ b/dom/base/Element.cpp
@@ -2461,6 +2461,9 @@ Element::SetAttr(int32_t aNamespaceID, nsIAtom* aName,
 
   uint8_t modType;
   bool hasListeners;
+  // We don't want to spend time preparsing class attributes if the value is not
+  // changing, so just init our nsAttrValueOrString with aValue for the
+  // OnlyNotifySameValueSet call.
   nsAttrValueOrString value(aValue);
   nsAttrValue oldValue;
 
@@ -2469,25 +2472,30 @@ Element::SetAttr(int32_t aNamespaceID, nsIAtom* aName,
     return NS_OK;
   }
 
-  nsresult rv = BeforeSetAttr(aNamespaceID, aName, &value, aNotify);
-  NS_ENSURE_SUCCESS(rv, rv);
-  nsAttrValue* preparsedAttrValue = value.GetStoredAttrValue();
+  nsAttrValue attrValue;
+  nsAttrValue* preparsedAttrValue;
+  if (aNamespaceID == kNameSpaceID_None && aName == nsGkAtoms::_class) {
+    attrValue.ParseAtomArray(aValue);
+    value.ResetToAttrValue(attrValue);
+    preparsedAttrValue = &attrValue;
+  } else {
+    preparsedAttrValue = nullptr;
+  }
 
   if (aNotify) {
     nsNodeUtils::AttributeWillChange(this, aNamespaceID, aName, modType,
                                      preparsedAttrValue);
   }
 
+  nsresult rv = BeforeSetAttr(aNamespaceID, aName, &value, aNotify);
+  NS_ENSURE_SUCCESS(rv, rv);
+
   // Hold a script blocker while calling ParseAttribute since that can call
   // out to id-observers
   nsAutoScriptBlocker scriptBlocker;
 
-  nsAttrValue attrValue;
-  if (preparsedAttrValue) {
-    attrValue.SwapValueWith(*preparsedAttrValue);
-  }
-  // Even the value was pre-parsed in BeforeSetAttr, we still need to call
-  // ParseAttribute because it can have side effects.
+  // Even the value was pre-parsed, we still need to call ParseAttribute because
+  // it can have side effects.
   if (!ParseAttribute(aNamespaceID, aName, aValue, attrValue)) {
     attrValue.SetTo(aValue);
   }
@@ -2523,14 +2531,14 @@ Element::SetParsedAttr(int32_t aNamespaceID, nsIAtom* aName,
     return NS_OK;
   }
 
-  nsresult rv = BeforeSetAttr(aNamespaceID, aName, &value, aNotify);
-  NS_ENSURE_SUCCESS(rv, rv);
-
   if (aNotify) {
     nsNodeUtils::AttributeWillChange(this, aNamespaceID, aName, modType,
                                      &aParsedValue);
   }
 
+  nsresult rv = BeforeSetAttr(aNamespaceID, aName, &value, aNotify);
+  NS_ENSURE_SUCCESS(rv, rv);
+
   return SetAttrAndNotify(aNamespaceID, aName, aPrefix, oldValue,
                           aParsedValue, modType, hasListeners, aNotify,
                           kCallAfterSetAttr);
@@ -2599,8 +2607,6 @@ Element::SetAttrAndNotify(int32_t aNamespaceID,
     }
   }
 
-  UpdateState(aNotify);
-
   if (CustomElementRegistry::IsCustomElementEnabled()) {
     if (CustomElementData* data = GetCustomElementData()) {
       if (CustomElementDefinition* definition =
@@ -2639,6 +2645,8 @@ Element::SetAttrAndNotify(int32_t aNamespaceID,
     }
   }
 
+  UpdateState(aNotify);
+
   if (aNotify) {
     // Don't pass aOldValue to AttributeChanged since it may not be reliable.
     // Callers only compute aOldValue under certain conditions which may not
@@ -2674,25 +2682,6 @@ Element::SetAttrAndNotify(int32_t aNamespaceID,
   return NS_OK;
 }
 
-nsresult
-Element::BeforeSetAttr(int32_t aNamespaceID, nsIAtom* aName,
-                       nsAttrValueOrString* aValue, bool aNotify)
-{
-  if (aNamespaceID == kNameSpaceID_None) {
-    if (aName == nsGkAtoms::_class) {
-      // aValue->GetAttrValue will only be non-null here when this is called
-      // via Element::SetParsedAttr. This shouldn't happen for "class", but
-      // this will handle it.
-      if (aValue && !aValue->GetAttrValue()) {
-        nsAttrValue attr;
-        attr.ParseAtomArray(aValue->String());
-        aValue->TakeParsedValue(attr);
-      }
-    }
-  }
-  return NS_OK;
-}
-
 bool
 Element::ParseAttribute(int32_t aNamespaceID,
                         nsIAtom* aAttribute,
@@ -2809,9 +2798,6 @@ Element::UnsetAttr(int32_t aNameSpaceID, nsIAtom* aName,
     return NS_OK;
   }
 
-  nsresult rv = BeforeSetAttr(aNameSpaceID, aName, nullptr, aNotify);
-  NS_ENSURE_SUCCESS(rv, rv);
-
   nsIDocument *document = GetComposedDoc();
   mozAutoDocUpdate updateBatch(document, UPDATE_CONTENT_MODEL, aNotify);
 
@@ -2821,6 +2807,9 @@ Element::UnsetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                                      nullptr);
   }
 
+  nsresult rv = BeforeSetAttr(aNameSpaceID, aName, nullptr, aNotify);
+  NS_ENSURE_SUCCESS(rv, rv);
+
   bool hasMutationListeners = aNotify &&
     nsContentUtils::HasMutationListeners(this,
                                          NS_EVENT_BITS_MUTATION_ATTRMODIFIED,
@@ -2869,8 +2858,6 @@ Element::UnsetAttr(int32_t aNameSpaceID, nsIAtom* aName,
     }
   }
 
-  UpdateState(aNotify);
-
   if (CustomElementRegistry::IsCustomElementEnabled()) {
     if (CustomElementData* data = GetCustomElementData()) {
       if (CustomElementDefinition* definition =
@@ -2897,6 +2884,11 @@ Element::UnsetAttr(int32_t aNameSpaceID, nsIAtom* aName,
     }
   }
 
+  rv = AfterSetAttr(aNameSpaceID, aName, nullptr, aNotify);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  UpdateState(aNotify);
+
   if (aNotify) {
     // We can always pass oldValue here since there is no new value which could
     // have corrupted it.
@@ -2904,9 +2896,6 @@ Element::UnsetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                                   nsIDOMMutationEvent::REMOVAL, &oldValue);
   }
 
-  rv = AfterSetAttr(aNameSpaceID, aName, nullptr, aNotify);
-  NS_ENSURE_SUCCESS(rv, rv);
-
   if (aNameSpaceID == kNameSpaceID_None && aName == nsGkAtoms::dir) {
     OnSetDirAttr(this, nullptr, hadValidDir, hadDirAuto, aNotify);
   }
diff --git a/dom/base/Element.h b/dom/base/Element.h
index 8139236aa8..aa917bffc8 100644
--- a/dom/base/Element.h
+++ b/dom/base/Element.h
@@ -1336,16 +1336,17 @@ protected:
    * @param aName the localname of the attribute being set
    * @param aValue the value it's being set to represented as either a string or
    *        a parsed nsAttrValue. Alternatively, if the attr is being removed it
-   *        will be null. BeforeSetAttr is allowed to modify aValue by parsing
-   *        the string to an nsAttrValue (to avoid having to reparse it in
-   *        ParseAttribute).
+   *        will be null.
    * @param aNotify Whether we plan to notify document observers.
    */
   // Note that this is inlined so that when subclasses call it it gets
   // inlined.  Those calls don't go through a vtable.
   virtual nsresult BeforeSetAttr(int32_t aNamespaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
-                                 bool aNotify);
+                                 const nsAttrValueOrString* aValue,
+                                 bool aNotify)
+  {
+    return NS_OK;
+  }
 
   /**
    * Hook that is called by Element::SetAttr to allow subclasses to
diff --git a/dom/base/nsAttrValueOrString.h b/dom/base/nsAttrValueOrString.h
index df0dac17de..8e6c069532 100644
--- a/dom/base/nsAttrValueOrString.h
+++ b/dom/base/nsAttrValueOrString.h
@@ -49,20 +49,13 @@ public:
     , mCheapString(nullptr)
   { }
 
-  void TakeParsedValue(nsAttrValue& aValue)
+  void ResetToAttrValue(const nsAttrValue& aValue)
   {
-    mStoredAttrValue.SwapValueWith(aValue);
-    mAttrValue = &mStoredAttrValue;
+    mAttrValue = &aValue;
     mStringPtr = nullptr;
+    // No need to touch mCheapString here.  If we need to use it, we will reset
+    // it to the rigthe value anyway.
   }
-  /**
-   * If TakeParsedValue has been called, returns the value that it set.
-   */
-  nsAttrValue* GetStoredAttrValue()
-  {
-    return mAttrValue == &mStoredAttrValue ? &mStoredAttrValue : nullptr;
-  }
-  const nsAttrValue* GetAttrValue() { return mAttrValue; }
 
   /**
    * Returns a reference to the string value of the contents of this object.
@@ -89,7 +82,6 @@ protected:
   const nsAttrValue*       mAttrValue;
   mutable const nsAString* mStringPtr;
   mutable nsCheapString    mCheapString;
-  nsAttrValue              mStoredAttrValue;
 };
 
 #endif // nsAttrValueOrString_h___
diff --git a/dom/html/HTMLButtonElement.cpp b/dom/html/HTMLButtonElement.cpp
index aad1c412bc..c26e60ed0f 100644
--- a/dom/html/HTMLButtonElement.cpp
+++ b/dom/html/HTMLButtonElement.cpp
@@ -423,7 +423,7 @@ HTMLButtonElement::DoneCreatingElement()
 
 nsresult
 HTMLButtonElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify)
 {
   if (aNotify && aName == nsGkAtoms::disabled &&
@@ -448,7 +448,6 @@ HTMLButtonElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
 
     if (aName == nsGkAtoms::type || aName == nsGkAtoms::disabled) {
       UpdateBarredFromConstraintValidation();
-      UpdateState(aNotify); 
     }
   }
 
diff --git a/dom/html/HTMLButtonElement.h b/dom/html/HTMLButtonElement.h
index a8d206dd69..19c93e4839 100644
--- a/dom/html/HTMLButtonElement.h
+++ b/dom/html/HTMLButtonElement.h
@@ -81,7 +81,7 @@ public:
    * Called when an attribute is about to be changed
    */
   virtual nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override;
   /**
    * Called when an attribute has just been changed
diff --git a/dom/html/HTMLDetailsElement.cpp b/dom/html/HTMLDetailsElement.cpp
index 8619b14508..9d4dd89c2a 100644
--- a/dom/html/HTMLDetailsElement.cpp
+++ b/dom/html/HTMLDetailsElement.cpp
@@ -45,7 +45,7 @@ HTMLDetailsElement::GetAttributeChangeHint(const nsIAtom* aAttribute,
 
 nsresult
 HTMLDetailsElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                  nsAttrValueOrString* aValue, bool aNotify)
+                                  const nsAttrValueOrString* aValue, bool aNotify)
 {
   if (aNameSpaceID == kNameSpaceID_None && aName == nsGkAtoms::open) {
     bool setOpen = aValue != nullptr;
diff --git a/dom/html/HTMLDetailsElement.h b/dom/html/HTMLDetailsElement.h
index 6adf567bf8..4575ed888d 100644
--- a/dom/html/HTMLDetailsElement.h
+++ b/dom/html/HTMLDetailsElement.h
@@ -38,7 +38,8 @@ public:
                                       int32_t aModType) const override;
 
   nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                         nsAttrValueOrString* aValue, bool aNotify) override;
+                         const nsAttrValueOrString* aValue,
+                         bool aNotify) override;
 
   // HTMLDetailsElement WebIDL
   bool Open() const { return GetBoolAttr(nsGkAtoms::open); }
diff --git a/dom/html/HTMLImageElement.cpp b/dom/html/HTMLImageElement.cpp
index 49cbebc5a4..5d0cfd15eb 100644
--- a/dom/html/HTMLImageElement.cpp
+++ b/dom/html/HTMLImageElement.cpp
@@ -369,7 +369,7 @@ HTMLImageElement::GetAttributeMappingFunction() const
 
 nsresult
 HTMLImageElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                nsAttrValueOrString* aValue,
+                                const nsAttrValueOrString* aValue,
                                 bool aNotify)
 {
 
diff --git a/dom/html/HTMLImageElement.h b/dom/html/HTMLImageElement.h
index 41730c2e5b..d92cd84b81 100644
--- a/dom/html/HTMLImageElement.h
+++ b/dom/html/HTMLImageElement.h
@@ -344,7 +344,7 @@ protected:
   void UpdateFormOwner();
 
   virtual nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override;
 
   virtual nsresult AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
diff --git a/dom/html/HTMLInputElement.cpp b/dom/html/HTMLInputElement.cpp
index d5fca28f6b..11ed3a5d48 100644
--- a/dom/html/HTMLInputElement.cpp
+++ b/dom/html/HTMLInputElement.cpp
@@ -1237,7 +1237,7 @@ HTMLInputElement::Clone(mozilla::dom::NodeInfo* aNodeInfo, nsINode** aResult) co
 
 nsresult
 HTMLInputElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                nsAttrValueOrString* aValue,
+                                const nsAttrValueOrString* aValue,
                                 bool aNotify)
 {
   if (aNameSpaceID == kNameSpaceID_None) {
@@ -1452,8 +1452,6 @@ HTMLInputElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
       // Clear the cached @autocomplete attribute state.
       mAutocompleteAttrState = nsContentUtils::eAutocompleteAttrState_Unknown;
     }
-
-    UpdateState(aNotify);
   }
 
   return nsGenericHTMLFormElementWithState::AfterSetAttr(aNameSpaceID, aName,
diff --git a/dom/html/HTMLInputElement.h b/dom/html/HTMLInputElement.h
index 98c74893e6..86bc7d0303 100644
--- a/dom/html/HTMLInputElement.h
+++ b/dom/html/HTMLInputElement.h
@@ -958,7 +958,7 @@ protected:
    * Called when an attribute is about to be changed
    */
   virtual nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override;
   /**
    * Called when an attribute has just been changed
diff --git a/dom/html/HTMLLinkElement.cpp b/dom/html/HTMLLinkElement.cpp
index 0a2cdaaf40..4c42d310a6 100644
--- a/dom/html/HTMLLinkElement.cpp
+++ b/dom/html/HTMLLinkElement.cpp
@@ -333,7 +333,7 @@ HTMLLinkElement::UpdateImport()
 
 nsresult
 HTMLLinkElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                               nsAttrValueOrString* aValue, bool aNotify)
+                               const nsAttrValueOrString* aValue, bool aNotify)
 {
   if (aNameSpaceID == kNameSpaceID_None &&
       (aName == nsGkAtoms::href || aName == nsGkAtoms::rel)) {
diff --git a/dom/html/HTMLLinkElement.h b/dom/html/HTMLLinkElement.h
index 1fa154f41e..9c69cfb13c 100644
--- a/dom/html/HTMLLinkElement.h
+++ b/dom/html/HTMLLinkElement.h
@@ -62,7 +62,7 @@ public:
   virtual void UnbindFromTree(bool aDeep = true,
                               bool aNullParent = true) override;
   virtual nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override;
   virtual nsresult AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                                 const nsAttrValue* aValue,
diff --git a/dom/html/HTMLOptionElement.cpp b/dom/html/HTMLOptionElement.cpp
index 7b1e3ca2d7..9d861d4145 100644
--- a/dom/html/HTMLOptionElement.cpp
+++ b/dom/html/HTMLOptionElement.cpp
@@ -181,7 +181,7 @@ HTMLOptionElement::GetAttributeChangeHint(const nsIAtom* aAttribute,
 
 nsresult
 HTMLOptionElement::BeforeSetAttr(int32_t aNamespaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify)
 {
   nsresult rv = nsGenericHTMLElement::BeforeSetAttr(aNamespaceID, aName,
diff --git a/dom/html/HTMLOptionElement.h b/dom/html/HTMLOptionElement.h
index 4b5e192ff5..23ef2fb5e6 100644
--- a/dom/html/HTMLOptionElement.h
+++ b/dom/html/HTMLOptionElement.h
@@ -47,7 +47,7 @@ public:
                                               int32_t aModType) const override;
 
   virtual nsresult BeforeSetAttr(int32_t aNamespaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override;
   virtual nsresult AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                                 const nsAttrValue* aValue, bool aNotify) override;
diff --git a/dom/html/HTMLSelectElement.cpp b/dom/html/HTMLSelectElement.cpp
index 272a165781..a5f88f3fb5 100644
--- a/dom/html/HTMLSelectElement.cpp
+++ b/dom/html/HTMLSelectElement.cpp
@@ -1269,7 +1269,7 @@ HTMLSelectElement::UnbindFromTree(bool aDeep, bool aNullParent)
 
 nsresult
 HTMLSelectElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify)
 {
   if (aNotify && aName == nsGkAtoms::disabled &&
@@ -1294,8 +1294,6 @@ HTMLSelectElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
       // Clear the cached @autocomplete attribute state
       mAutocompleteAttrState = nsContentUtils::eAutocompleteAttrState_Unknown;
     }
-
-    UpdateState(aNotify);
   }
 
   return nsGenericHTMLFormElementWithState::AfterSetAttr(aNameSpaceID, aName,
diff --git a/dom/html/HTMLSelectElement.h b/dom/html/HTMLSelectElement.h
index 4cb5f90c9f..8eb7fa410d 100644
--- a/dom/html/HTMLSelectElement.h
+++ b/dom/html/HTMLSelectElement.h
@@ -375,7 +375,7 @@ public:
                                bool aCompileEventHandlers) override;
   virtual void UnbindFromTree(bool aDeep, bool aNullParent) override;
   virtual nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override;
   virtual nsresult AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                                 const nsAttrValue* aValue, bool aNotify) override;
diff --git a/dom/html/HTMLTableElement.cpp b/dom/html/HTMLTableElement.cpp
index c5b7696cfd..5784fa6912 100644
--- a/dom/html/HTMLTableElement.cpp
+++ b/dom/html/HTMLTableElement.cpp
@@ -986,7 +986,7 @@ HTMLTableElement::UnbindFromTree(bool aDeep, bool aNullParent)
 
 nsresult
 HTMLTableElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                nsAttrValueOrString* aValue,
+                                const nsAttrValueOrString* aValue,
                                 bool aNotify)
 {
   if (aName == nsGkAtoms::cellpadding && aNameSpaceID == kNameSpaceID_None) {
diff --git a/dom/html/HTMLTableElement.h b/dom/html/HTMLTableElement.h
index 4e172964bf..cf83c9440d 100644
--- a/dom/html/HTMLTableElement.h
+++ b/dom/html/HTMLTableElement.h
@@ -190,7 +190,7 @@ public:
    * Called when an attribute is about to be changed
    */
   virtual nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override;
   /**
    * Called when an attribute has just been changed
diff --git a/dom/html/HTMLTextAreaElement.cpp b/dom/html/HTMLTextAreaElement.cpp
index 796d8a49e9..c929daebd9 100644
--- a/dom/html/HTMLTextAreaElement.cpp
+++ b/dom/html/HTMLTextAreaElement.cpp
@@ -1286,7 +1286,7 @@ HTMLTextAreaElement::UnbindFromTree(bool aDeep, bool aNullParent)
 
 nsresult
 HTMLTextAreaElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                   nsAttrValueOrString* aValue,
+                                   const nsAttrValueOrString* aValue,
                                    bool aNotify)
 {
   if (aNotify && aName == nsGkAtoms::disabled &&
@@ -1364,8 +1364,6 @@ HTMLTextAreaElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
     } else if (aName == nsGkAtoms::minlength) {
       UpdateTooShortValidityState();
     }
-
-    UpdateState(aNotify);
   }
 
   return nsGenericHTMLFormElementWithState::AfterSetAttr(aNameSpaceID, aName, aValue,
diff --git a/dom/html/HTMLTextAreaElement.h b/dom/html/HTMLTextAreaElement.h
index bfc7d203d8..8723e85f68 100644
--- a/dom/html/HTMLTextAreaElement.h
+++ b/dom/html/HTMLTextAreaElement.h
@@ -144,7 +144,7 @@ public:
    * Called when an attribute is about to be changed
    */
   virtual nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override;
 
   // nsIMutationObserver
diff --git a/dom/html/nsGenericHTMLElement.cpp b/dom/html/nsGenericHTMLElement.cpp
index 394a77a590..30ecd8508d 100644
--- a/dom/html/nsGenericHTMLElement.cpp
+++ b/dom/html/nsGenericHTMLElement.cpp
@@ -1962,7 +1962,7 @@ nsGenericHTMLFormElement::UnbindFromTree(bool aDeep, bool aNullParent)
 
 nsresult
 nsGenericHTMLFormElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                        nsAttrValueOrString* aValue,
+                                        const nsAttrValueOrString* aValue,
                                         bool aNotify)
 {
   if (aNameSpaceID == kNameSpaceID_None) {
@@ -1995,13 +1995,6 @@ nsGenericHTMLFormElement::BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
       }
 
       mForm->RemoveElement(this, false);
-
-      // Removing the element from the form can make it not be the default
-      // control anymore.  Go ahead and notify on that change, though we might
-      // end up readding and becoming the default control again in
-      // AfterSetAttr.
-      // FIXME: Bug 656197
-      UpdateState(aNotify);
     }
 
     if (aName == nsGkAtoms::form) {
@@ -2051,12 +2044,6 @@ nsGenericHTMLFormElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
       }
 
       mForm->AddElement(this, false, aNotify);
-
-      // Adding the element to the form can make it be the default control .
-      // Go ahead and notify on that change.
-      // Note: no need to notify on CanBeDisabled(), since type attr
-      // changes can't affect that.
-      UpdateState(aNotify);
     }
 
     if (aName == nsGkAtoms::form) {
diff --git a/dom/html/nsGenericHTMLElement.h b/dom/html/nsGenericHTMLElement.h
index ab4391aa1e..a8a0d2596c 100644
--- a/dom/html/nsGenericHTMLElement.h
+++ b/dom/html/nsGenericHTMLElement.h
@@ -1263,7 +1263,7 @@ protected:
   virtual ~nsGenericHTMLFormElement();
 
   virtual nsresult BeforeSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override;
 
   virtual nsresult AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
diff --git a/dom/svg/nsSVGElement.cpp b/dom/svg/nsSVGElement.cpp
index ce849acf0f..9099caaaa0 100644
--- a/dom/svg/nsSVGElement.cpp
+++ b/dom/svg/nsSVGElement.cpp
@@ -1441,27 +1441,16 @@ nsSVGElement::WillChangeValue(nsIAtom* aName)
   // We need an empty attr value:
   //   a) to pass to BeforeSetAttr when GetParsedAttr returns nullptr
   //   b) to store the old value in the case we have mutation listeners
-  // We can use the same value for both purposes since (a) happens before (b).
+  //
+  // We can use the same value for both purposes, because if GetParsedAttr
+  // returns non-null its return value is what will get passed to BeforeSetAttr,
+  // not matter what our mutation listener situation is.
+  //
   // Also, we should be careful to always return this value to benefit from
   // return value optimization.
   nsAttrValue emptyOrOldAttrValue;
   const nsAttrValue* attrValue = GetParsedAttr(aName);
 
-  // This is not strictly correct--the attribute value parameter for
-  // BeforeSetAttr should reflect the value that *will* be set but that implies
-  // allocating, e.g. an extra nsSVGLength2, and isn't necessary at the moment
-  // since no SVG elements overload BeforeSetAttr. For now we just pass the
-  // current value.
-  nsAttrValueOrString attrStringOrValue(attrValue ? *attrValue
-                                                  : emptyOrOldAttrValue);
-  DebugOnly<nsresult> rv =
-    BeforeSetAttr(kNameSpaceID_None, aName, &attrStringOrValue,
-                  kNotifyDocumentObservers);
-  // SVG elements aren't expected to overload BeforeSetAttr in such a way that
-  // it may fail. So long as this is the case we don't need to check and pass on
-  // the return value which simplifies the calling code significantly.
-  MOZ_ASSERT(NS_SUCCEEDED(rv), "Unexpected failure from BeforeSetAttr");
-
   // We only need to set the old value if we have listeners since otherwise it
   // isn't used.
   if (attrValue &&
@@ -1477,6 +1466,21 @@ nsSVGElement::WillChangeValue(nsIAtom* aName)
   nsNodeUtils::AttributeWillChange(this, kNameSpaceID_None, aName, modType,
                                    nullptr);
 
+  // This is not strictly correct--the attribute value parameter for
+  // BeforeSetAttr should reflect the value that *will* be set but that implies
+  // allocating, e.g. an extra nsSVGLength2, and isn't necessary at the moment
+  // since no SVG elements overload BeforeSetAttr. For now we just pass the
+  // current value.
+  nsAttrValueOrString attrStringOrValue(attrValue ? *attrValue
+                                                  : emptyOrOldAttrValue);
+  DebugOnly<nsresult> rv =
+    BeforeSetAttr(kNameSpaceID_None, aName, &attrStringOrValue,
+                  kNotifyDocumentObservers);
+  // SVG elements aren't expected to overload BeforeSetAttr in such a way that
+  // it may fail. So long as this is the case we don't need to check and pass on
+  // the return value which simplifies the calling code significantly.
+  MOZ_ASSERT(NS_SUCCEEDED(rv), "Unexpected failure from BeforeSetAttr");
+
   return emptyOrOldAttrValue;
 }
 
diff --git a/dom/svg/nsSVGElement.h b/dom/svg/nsSVGElement.h
index 257ed7a2e6..79278365aa 100644
--- a/dom/svg/nsSVGElement.h
+++ b/dom/svg/nsSVGElement.h
@@ -329,7 +329,7 @@ protected:
   // BeforeSetAttr since it would involve allocating extra SVG value types.
   // See the comment in nsSVGElement::WillChangeValue.
   virtual nsresult BeforeSetAttr(int32_t aNamespaceID, nsIAtom* aName,
-                                 nsAttrValueOrString* aValue,
+                                 const nsAttrValueOrString* aValue,
                                  bool aNotify) override final
   {
     return nsSVGElementBase::BeforeSetAttr(aNamespaceID, aName, aValue, aNotify);
diff --git a/dom/xul/nsXULElement.cpp b/dom/xul/nsXULElement.cpp
index c7a5393707..e96bbeef44 100644
--- a/dom/xul/nsXULElement.cpp
+++ b/dom/xul/nsXULElement.cpp
@@ -1007,7 +1007,7 @@ nsXULElement::UnregisterAccessKey(const nsAString& aOldValue)
 
 nsresult
 nsXULElement::BeforeSetAttr(int32_t aNamespaceID, nsIAtom* aName,
-                            nsAttrValueOrString* aValue, bool aNotify)
+                            const nsAttrValueOrString* aValue, bool aNotify)
 {
     if (aNamespaceID == kNameSpaceID_None && aName == nsGkAtoms::accesskey &&
         IsInUncomposedDoc()) {
diff --git a/dom/xul/nsXULElement.h b/dom/xul/nsXULElement.h
index 109f6c2e75..c2dcadf5f8 100644
--- a/dom/xul/nsXULElement.h
+++ b/dom/xul/nsXULElement.h
@@ -624,7 +624,7 @@ protected:
     nsresult MakeHeavyweight(nsXULPrototypeElement* aPrototype);
 
     virtual nsresult BeforeSetAttr(int32_t aNamespaceID, nsIAtom* aName,
-                                   nsAttrValueOrString* aValue,
+                                   const nsAttrValueOrString* aValue,
                                    bool aNotify) override;
     virtual nsresult AfterSetAttr(int32_t aNamespaceID, nsIAtom* aName,
                                   const nsAttrValue* aValue, bool aNotify) override;