Issue %3024 - First pass support for :host and :host-context

8 files changed, 291 insertions, 25 deletions

diff --git a/layout/style/StyleRule.cpp b/layout/style/StyleRule.cpp
index 6fad62f8b..c8f1a0a91 100644
--- a/layout/style/StyleRule.cpp
+++ b/layout/style/StyleRule.cpp
@@ -148,7 +148,8 @@ nsPseudoClassList::nsPseudoClassList(CSSPseudoClassType aType,
   : mType(aType),
     mNext(nullptr)
 {
-  NS_ASSERTION(nsCSSPseudoClasses::HasSelectorListArg(aType),
+  NS_ASSERTION(nsCSSPseudoClasses::HasSelectorListArg(aType) ||
+	       nsCSSPseudoClasses::HasOptionalSelectorListArg(aType),
                "unexpected pseudo-class");
   NS_ASSERTION(aSelectorList, "selector list expected");
   MOZ_COUNT_CTOR(nsPseudoClassList);
@@ -313,6 +314,7 @@ nsCSSSelector::nsCSSSelector(void)
     mPseudoClassList(nullptr),
     mAttrList(nullptr),
     mNegations(nullptr),
+    mExplicitUniversal(false),
     mNext(nullptr),
     mNameSpace(kNameSpaceID_Unknown),
     mOperator(0),
@@ -382,6 +384,17 @@ void nsCSSSelector::Reset(void)
   mOperator = char16_t(0);
 }
 
+bool nsCSSSelector::HasFeatureSelectors()
+{
+  return mExplicitUniversal || mLowercaseTag || mCasedTag ||
+    mIDList || mClassList || mAttrList;
+}
+
+void nsCSSSelector::SetHasExplicitUniversal()
+{
+  mExplicitUniversal = true;
+}
+
 void nsCSSSelector::SetNameSpace(int32_t aNameSpace)
 {
   mNameSpace = aNameSpace;
@@ -742,9 +755,9 @@ nsCSSSelector::AppendToStringWithoutCombinatorsOrNegations
     // Universal selector:  avoid writing the universal selector when we
     // can avoid it, especially since we're required to avoid it for the
     // inside of :not()
-    if (wroteNamespace ||
+    if (wroteNamespace || mExplicitUniversal ||
         (!mIDList && !mClassList && !mPseudoClassList && !mAttrList &&
-         (aIsNegated || !mNegations))) {
+         aIsNegated)) {
       aString.Append(char16_t('*'));
     }
   } else {
@@ -752,9 +765,7 @@ nsCSSSelector::AppendToStringWithoutCombinatorsOrNegations
     nsAutoString tag;
     (isPseudoElement ? mLowercaseTag : mCasedTag)->ToString(tag);
     if (isPseudoElement) {
-      if (!mNext) {
-        // Lone pseudo-element selector -- toss in a wildcard type selector
-        // XXXldb Why?
+      if (mExplicitUniversal) {
         aString.Append(char16_t('*'));
       }
       // While our atoms use one colon, most pseudo-elements require two
diff --git a/layout/style/StyleRule.h b/layout/style/StyleRule.h
index 907e55448..dbf4e0840 100644
--- a/layout/style/StyleRule.h
+++ b/layout/style/StyleRule.h
@@ -151,6 +151,8 @@ public:
   nsCSSSelector* Clone() const { return Clone(true, true); }
 
   void Reset(void);
+  bool HasFeatureSelectors();
+  void SetHasExplicitUniversal();
   void SetNameSpace(int32_t aNameSpace);
   void SetTag(const nsString& aTag);
   void AddID(const nsString& aID);
@@ -231,9 +233,10 @@ public:
                                        // the argument to functional pseudos
   nsAttrSelector* mAttrList;
   nsCSSSelector*  mNegations;
-  nsCSSSelector*  mNext;
+  bool            mExplicitUniversal; // True if universal selector explicitly
+  nsCSSSelector*  mNext;              // appears in the selector
   int32_t         mNameSpace;
-  char16_t       mOperator;
+  char            mOperator;
 private:
   // The underlying type of CSSPseudoElementType is uint8_t and
   // it packs well with mOperator. (char16_t + uint8_t is less than 32bits.)
diff --git a/layout/style/nsCSSParser.cpp b/layout/style/nsCSSParser.cpp
index 3d5edbd0e..2e2700c38 100644
--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -5639,6 +5639,7 @@ CSSParserImpl::ParseTypeOrUniversalSelector(int32_t&       aDataMask,
         aSelector.SetTag(mToken.mIdent);
       }
       else if (mToken.IsSymbol('*')) {  // universal selector
+	aSelector.SetHasExplicitUniversal();
         aDataMask |= SEL_MASK_ELEM;
         // don't set tag
       }
@@ -5650,6 +5651,7 @@ CSSParserImpl::ParseTypeOrUniversalSelector(int32_t&       aDataMask,
     }
     else {  // was universal element selector
       SetDefaultNamespaceOnSelector(aSelector);
+      aSelector.SetHasExplicitUniversal();
       aDataMask |= SEL_MASK_ELEM;
       // don't set any tag in the selector
     }
@@ -6089,7 +6091,8 @@ CSSParserImpl::ParsePseudoSelector(int32_t&       aDataMask,
        CSSPseudoClassType::negation == pseudoClassType ||
        nsCSSPseudoClasses::HasStringArg(pseudoClassType) ||
        nsCSSPseudoClasses::HasNthPairArg(pseudoClassType) ||
-       nsCSSPseudoClasses::HasSelectorListArg(pseudoClassType))) {
+       nsCSSPseudoClasses::HasSelectorListArg(pseudoClassType)) &&
+       !nsCSSPseudoClasses::HasOptionalSelectorListArg(pseudoClassType)) {
     // There are no other function pseudos
     REPORT_UNEXPECTED_TOKEN(PEPseudoSelNonFunc);
     UngetToken();
diff --git a/layout/style/nsCSSPseudoClassList.h b/layout/style/nsCSSPseudoClassList.h
index 7f620ec32..c57c28bc0 100644
--- a/layout/style/nsCSSPseudoClassList.h
+++ b/layout/style/nsCSSPseudoClassList.h
@@ -133,6 +133,12 @@ CSS_PSEUDO_CLASS(scope, ":scope", 0, "layout.css.scope-pseudo.enabled")
 // it doesn't actually get directly matched on in SelectorMatches.
 CSS_PSEUDO_CLASS(negation, ":not", 0, "")
 
+// http://drafts.csswg.org/css-scoping/#selectordef-host-context
+CSS_PSEUDO_CLASS(hostContext, ":host-context", 0, "dom.webcomponents.enabled")
+
+// http://drafts.csswg.org/css-scoping/#selectordef-host-context
+CSS_PSEUDO_CLASS(host, ":host", 0, "dom.webcomponents.enabled")
+
 // :dir(ltr) and :dir(rtl) match elements whose resolved
 // directionality in the markup language is ltr or rtl respectively.
 CSS_STATE_DEPENDENT_PSEUDO_CLASS(dir, ":dir", 0, "",
diff --git a/layout/style/nsCSSPseudoClasses.h b/layout/style/nsCSSPseudoClasses.h
index 55e5bf9d2..05f67b05c 100644
--- a/layout/style/nsCSSPseudoClasses.h
+++ b/layout/style/nsCSSPseudoClasses.h
@@ -59,7 +59,12 @@ public:
   static bool HasStringArg(Type aType);
   static bool HasNthPairArg(Type aType);
   static bool HasSelectorListArg(Type aType) {
-    return aType == Type::any;
+    return aType == Type::any ||
+	   aType == Type::host ||
+	   aType == Type::hostContext;
+  }
+  static bool HasOptionalSelectorListArg(Type aType) {
+    return aType == Type::host;
   }
   static bool IsUserActionPseudoClass(Type aType);
 
diff --git a/layout/style/nsCSSRuleProcessor.cpp b/layout/style/nsCSSRuleProcessor.cpp
index aed26a1c0..f49b9d325 100644
--- a/layout/style/nsCSSRuleProcessor.cpp
+++ b/layout/style/nsCSSRuleProcessor.cpp
@@ -48,6 +48,7 @@
 #include "nsCSSRules.h"
 #include "nsStyleSet.h"
 #include "mozilla/dom/Element.h"
+#include "mozilla/dom/ShadowRoot.h"
 #include "nsNthIndexCache.h"
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/EventStates.h"
@@ -1321,9 +1322,17 @@ struct NodeMatchContext {
   // mForStyling is false, we have to assume we don't know.)
   const bool mIsRelevantLink;
 
-  NodeMatchContext(EventStates aStateMask, bool aIsRelevantLink)
+  // If the node should be considered featureless (as specified in
+  // selectors 4), then mIsFeature should be set to true to prevent
+  // matching unless the selector is a special pseudo class or pseudo
+  // element that matches featureless elements.
+  const bool mIsFeatureless;
+
+  NodeMatchContext(EventStates aStateMask, bool aIsRelevantLink,
+                   bool aIsFeatureless = false)
     : mStateMask(aStateMask)
     , mIsRelevantLink(aIsRelevantLink)
+    , mIsFeatureless(aIsFeatureless)
   {
   }
 };
@@ -1610,6 +1619,11 @@ StateSelectorMatches(Element* aElement,
   return true;
 }
 
+static bool AnySelectorInArgListMatches(Element* aElement,
+                                     nsPseudoClassList* aList,
+                                     NodeMatchContext& aNodeMatchContext,
+                                     TreeMatchContext& aTreeMatchContext);
+
 static bool
 StateSelectorMatches(Element* aElement,
                      nsCSSSelector* aSelector,
@@ -1631,6 +1645,26 @@ StateSelectorMatches(Element* aElement,
   return true;
 }
 
+// Returns whether aSelector can match featureless elements.
+static bool CanMatchFeaturelessElement(nsCSSSelector* aSelector)
+{
+  if (aSelector->HasFeatureSelectors()) {
+    return false;
+  }
+
+  for (nsPseudoClassList* pseudoClass = aSelector->mPseudoClassList;
+       pseudoClass;
+       pseudoClass = pseudoClass->mNext) {
+    if (pseudoClass->mType == CSSPseudoClassType::host ||
+        pseudoClass->mType == CSSPseudoClassType::hostContext) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+
 // |aDependence| has two functions:
 //  * when non-null, it indicates that we're processing a negation,
 //    which is done only when SelectorMatches calls itself recursively
@@ -1651,6 +1685,11 @@ static bool SelectorMatches(Element* aElement,
              "is false since we don't know how to set it correctly in "
              "Has(Attribute|State)DependentStyle");
 
+  if (aNodeMatchContext.mIsFeatureless &&
+      !CanMatchFeaturelessElement(aSelector)) {
+    return false;
+  }
+
   // namespace/tag match
   // optimization : bail out early if we can
   if ((kNameSpaceID_Unknown != aSelector->mNameSpace &&
@@ -1849,18 +1888,89 @@ static bool SelectorMatches(Element* aElement,
 
       case CSSPseudoClassType::any:
         {
-          nsCSSSelectorList *l;
-          for (l = pseudoClass->u.mSelectors; l; l = l->mNext) {
-            nsCSSSelector *s = l->mSelectors;
-            MOZ_ASSERT(!s->mNext && !s->IsPseudoElement(),
-                       "parser failed");
-            if (SelectorMatches(
-                  aElement, s, aNodeMatchContext, aTreeMatchContext,
-                  SelectorMatchesFlags::IS_PSEUDO_CLASS_ARGUMENT)) {
+          if (!AnySelectorInArgListMatches(aElement, pseudoClass,
+                                           aNodeMatchContext,
+                                           aTreeMatchContext)) {
+            return false;
+          }
+        }
+        break;
+
+      case CSSPseudoClassType::host:
+        {
+          // In order to match :host, the element must be a shadow root host,
+          // we must be matching only against host pseudo selectors, and the 
+          // selector's context must be the shadow root (the selector must be 
+          // featureless, the left-most selector, and be in a shadow root 
+          // style). The :host selector may also be be functional, with a 
+          // compound selector. If this is the case, then also ensure that the 
+          // host element matches against the compound
+          // selector.
+           
+          // We match automatically if GetParent() and GetShadowRoot() have 
+          // the same result. Without special casing this ahead of all other 
+          // selector matching, it fails. Have not determined the cause.
+
+          if (aElement->GetParent() == aElement->GetShadowRoot()) {
+            break;
+          }
+
+          // Match if any selector in the argument list matches.
+
+          NodeMatchContext nodeContext(EventStates(),
+                               nsCSSRuleProcessor::IsLink(aElement));
+          if (AnySelectorInArgListMatches(aElement, pseudoClass,
+                                            nodeContext,
+                                            aTreeMatchContext)) {
+            break;
+          }
+
+          // Finally, with the exception of the two above cases, make sure we 
+          // don't match if GetContainingShadow() returns null. For whatever 
+          // reason, we can't test for this case first. 
+
+          if (aElement->GetContainingShadow() == nullptr) {
+            return false;
+          }
+          
+        }
+        break;
+
+
+      case CSSPseudoClassType::hostContext:
+        {
+          // In order to match host-context, the element must be a
+          // shadow root host and the selector's context must be the
+          // shadow root (aTreeMatchContext.mScopedRoot is set to the
+          // host of the shadow root where the style is contained,
+          // thus the element must be mScopedRoot). If the UNKNOWN
+          // selector flag is set, relax the shadow root host
+          // requirement because this pseudo class walks through
+          // ancestors looking for a match, thus the selector can be
+          // dependant on aElement even though it is not the host. The
+          // dependency would otherwise be missed because when UNKNOWN
+          // is set, selector matching may not have started from the top.
+          if (!((aElement->GetShadowRoot() &&
+                 aElement == aTreeMatchContext.mScopedRoot) ||
+                aSelectorFlags & SelectorMatchesFlags::UNKNOWN)) {
+            return false;
+          }
+
+          Element* currentElement = aElement;
+          while (currentElement) {
+            NodeMatchContext nodeContext(EventStates(),
+                               nsCSSRuleProcessor::IsLink(currentElement));
+            if (AnySelectorInArgListMatches(currentElement, pseudoClass,
+                                            nodeContext,
+                                            aTreeMatchContext)) {
               break;
             }
+
+            nsIContent* flattenedParent = currentElement->GetFlattenedTreeParent();
+            currentElement = flattenedParent && flattenedParent->IsElement() ?
+              flattenedParent->AsElement() : nullptr;
           }
-          if (!l) {
+          if (!currentElement) {
             return false;
           }
         }
@@ -2242,6 +2352,26 @@ static bool SelectorMatches(Element* aElement,
   return result;
 }
 
+static bool AnySelectorInArgListMatches(Element* aElement,
+                                     nsPseudoClassList* aList,
+                                     NodeMatchContext& aNodeMatchContext,
+                                     TreeMatchContext& aTreeMatchContext)
+{
+  nsCSSSelectorList *l;
+  for (l = aList->u.mSelectors; l; l = l->mNext) {
+    nsCSSSelector *s = l->mSelectors;
+    MOZ_ASSERT(!s->mNext && !s->IsPseudoElement(),
+           "parser failed");
+    if (SelectorMatches(
+          aElement, s, aNodeMatchContext, aTreeMatchContext,
+          SelectorMatchesFlags::IS_PSEUDO_CLASS_ARGUMENT)) {
+      break;
+    }
+  }
+
+  return !!l;
+}
+
 #undef STATE_CHECK
 
 #ifdef DEBUG
@@ -2331,7 +2461,9 @@ SelectorMatchesTree(Element* aPrevElement,
   MOZ_ASSERT(!aSelector || !aSelector->IsPseudoElement());
   nsCSSSelector* selector = aSelector;
   Element* prevElement = aPrevElement;
+  bool crossedShadowRootBoundary = false;
   while (selector) { // check compound selectors
+    bool contentIsFeatureless = false;
     NS_ASSERTION(!selector->mNext ||
                  selector->mNext->mOperator != char16_t(0),
                  "compound selector without combinator");
@@ -2362,6 +2494,20 @@ SelectorMatchesTree(Element* aPrevElement,
     // to test against is the parent
     else {
       nsIContent *content = prevElement->GetParent();
+
+      // In the shadow tree, the shadow host behaves as if it
+      // is a featureless parent of top-level elements of the shadow
+      // tree. Only cross shadow root boundary when the selector is the
+      // left most selector because ancestors of the host are not in
+      // the selector match list.
+      ShadowRoot* shadowRoot = content ?
+        ShadowRoot::FromNode(content) : nullptr;
+      if (shadowRoot && !selector->mNext && !crossedShadowRootBoundary) {
+      content = shadowRoot->GetHost();
+      crossedShadowRootBoundary = true;
+      contentIsFeatureless = true;
+      }
+
       // GetParent could return a document fragment; we only want
       // element parents.
       if (content && content->IsElement()) {
@@ -2413,7 +2559,8 @@ SelectorMatchesTree(Element* aPrevElement,
     }
     const bool isRelevantLink = (aFlags & eLookForRelevantLink) &&
                                 nsCSSRuleProcessor::IsLink(element);
-    NodeMatchContext nodeContext(EventStates(), isRelevantLink);
+
+    NodeMatchContext nodeContext(EventStates(), isRelevantLink, contentIsFeatureless);
     if (isRelevantLink) {
       // If we find an ancestor of the matched node that is a link
       // during the matching process, then it's the relevant link (see
@@ -2483,6 +2630,29 @@ void ContentEnumFunc(const RuleValue& value, nsCSSSelector* aSelector,
     // We won't match; nothing else to do here
     return;
   }
+  // If mOnlyMatchHostPseudo is set, then we only want to match against
+  // selectors that contain a :host-context pseudo class.
+  if (data->mTreeMatchContext.mOnlyMatchHostPseudo) {
+    nsCSSSelector* selector = aSelector;
+    while (selector && selector->mNext != nullptr) {
+      selector = selector->mNext;
+    }
+
+    bool seenHostPseudo = false;
+    for (nsPseudoClassList* pseudoClass = selector->mPseudoClassList;
+         pseudoClass;
+         pseudoClass = pseudoClass->mNext) {
+      if (pseudoClass->mType == CSSPseudoClassType::host ||
+	        pseudoClass->mType == CSSPseudoClassType::hostContext) {
+        seenHostPseudo = true;
+        break;
+      }
+    }
+
+    if (!seenHostPseudo) {
+      return;
+    }
+  }
   if (!data->mTreeMatchContext.SetStyleScopeForSelectorMatching(data->mElement,
                                                                 data->mScope)) {
     // The selector is for a rule in a scoped style sheet, and the subject
@@ -2542,7 +2712,8 @@ nsCSSRuleProcessor::RulesMatching(ElementRuleProcessorData *aData)
 
   if (cascade) {
     NodeMatchContext nodeContext(EventStates(),
-                                 nsCSSRuleProcessor::IsLink(aData->mElement));
+                                 nsCSSRuleProcessor::IsLink(aData->mElement),
+				 aData->mElementIsFeatureless);
     cascade->mRuleHash.EnumerateAllRules(aData->mElement, aData, nodeContext);
   }
 }
@@ -2824,6 +2995,34 @@ AttributeEnumFunc(nsCSSSelector* aSelector,
   nsRestyleHint possibleChange =
     RestyleHintForSelectorWithAttributeChange(aData->change,
                                               aSelector, aRightmostSelector);
+  // If mOnlyMatchHostPseudo is set, then we only want to match against
+  // selectors that contain a :host-context pseudo class.
+  if (data->mTreeMatchContext.mOnlyMatchHostPseudo) {
+    nsCSSSelector* selector = aSelector;
+    while (selector && selector->mNext != nullptr) {
+      selector = selector->mNext;
+    }
+
+    bool seenHostPseudo = false;
+    for (nsPseudoClassList* pseudoClass = selector->mPseudoClassList;
+         pseudoClass;
+         pseudoClass = pseudoClass->mNext) {
+      if (pseudoClass->mType == CSSPseudoClassType::host ||
+	        pseudoClass->mType == CSSPseudoClassType::hostContext) {
+        // :host-context will walk ancestors looking for a match of a compound 
+        // selector, thus any changes to ancestors may require restyling the 
+        // subtree.
+        possibleChange |= eRestyle_Subtree;
+        seenHostPseudo = true;
+        break;
+      }
+    }
+
+    if (!seenHostPseudo) {
+      return;
+    }
+  }
+
 
   // If, ignoring eRestyle_SomeDescendants, enumData->change already includes
   // all the bits of possibleChange, don't bother calling SelectorMatches, since
@@ -3295,10 +3494,12 @@ AddSelector(RuleCascadeData* aCascade,
       }
     }
 
-    // Recur through any :-moz-any selectors
+    // Recur through any :-moz-any or :host-context selectors
     for (nsPseudoClassList* pseudoClass = negation->mPseudoClassList;
          pseudoClass; pseudoClass = pseudoClass->mNext) {
-      if (pseudoClass->mType == CSSPseudoClassType::any) {
+      if (pseudoClass->mType == CSSPseudoClassType::any ||
+          pseudoClass->mType == CSSPseudoClassType::host ||
+          pseudoClass->mType == CSSPseudoClassType::hostContext) {
         for (nsCSSSelectorList *l = pseudoClass->u.mSelectors; l; l = l->mNext) {
           nsCSSSelector *s = l->mSelectors;
           if (!AddSelector(aCascade, aSelectorInTopLevel, s,
@@ -3943,6 +4144,7 @@ TreeMatchContext::InitAncestors(Element *aElement)
     for (uint32_t i = ancestors.Length(); i-- != 0; ) {
       mAncestorFilter.PushAncestor(ancestors[i]);
       PushStyleScope(ancestors[i]);
+      PushShadowHost(ancestors[i]);
     }
   }
 }
diff --git a/layout/style/nsRuleProcessorData.h b/layout/style/nsRuleProcessorData.h
index fbaa768cc..f6d977100 100644
--- a/layout/style/nsRuleProcessorData.h
+++ b/layout/style/nsRuleProcessorData.h
@@ -164,6 +164,23 @@ struct MOZ_STACK_CLASS TreeMatchContext {
       mStyleScopes.TruncateLength(mStyleScopes.Length() - 1);
     }
   }
+
+  void PushShadowHost(mozilla::dom::Element* aElement)
+  {
+    NS_PRECONDITION(aElement, "aElement must not be null");
+    if (aElement->GetShadowRoot()) {
+      mShadowHosts.AppendElement(aElement);
+    }
+  }
+
+  void PopShadowHost(mozilla::dom::Element* aElement)
+  {
+    NS_PRECONDITION(aElement, "aElement must not be null");
+    if (mShadowHosts.SafeLastElement(nullptr) == aElement) {
+      mShadowHosts.TruncateLength(mShadowHosts.Length() - 1);
+    }
+  }
+
  
   bool PopStyleScopeForSelectorMatching(mozilla::dom::Element* aElement)
   {
@@ -233,6 +250,7 @@ struct MOZ_STACK_CLASS TreeMatchContext {
                                 MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
       : mPushedAncestor(false)
       , mPushedStyleScope(false)
+      , mPushedShadowHost(false)
       , mTreeMatchContext(aTreeMatchContext)
       , mElement(nullptr)
     {
@@ -245,8 +263,10 @@ struct MOZ_STACK_CLASS TreeMatchContext {
         mElement = aElement;
         mPushedAncestor = true;
         mPushedStyleScope = true;
+	mPushedShadowHost = true;
         mTreeMatchContext.mAncestorFilter.PushAncestor(aElement);
         mTreeMatchContext.PushStyleScope(aElement);
+	mTreeMatchContext.PushShadowHost(aElement);
       }
     }
 
@@ -278,11 +298,15 @@ struct MOZ_STACK_CLASS TreeMatchContext {
       if (mPushedStyleScope) {
         mTreeMatchContext.PopStyleScope(mElement);
       }
+      if (mPushedShadowHost) {
+	mTreeMatchContext.PopShadowHost(mElement);
+      }
     }
 
   private:
     bool mPushedAncestor;
     bool mPushedStyleScope;
+    bool mPushedShadowHost;
     TreeMatchContext& mTreeMatchContext;
     mozilla::dom::Element* mElement;
     MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
@@ -342,6 +366,11 @@ struct MOZ_STACK_CLASS TreeMatchContext {
   // The document we're working with.
   nsIDocument* const mDocument;
 
+  // Only selectors that contain :host or :host-context pseudo class
+  // should be matched against elements. All other selectors should not
+  // match.
+  bool mOnlyMatchHostPseudo;
+
   // Root of scoped stylesheet (set and unset by the supplier of the
   // scoped stylesheet).
   nsIContent* mScopedRoot;
@@ -383,6 +412,9 @@ struct MOZ_STACK_CLASS TreeMatchContext {
   // <style scoped> child).
   AutoTArray<mozilla::dom::Element*, 1> mStyleScopes;
 
+  // List of ancestor elements that are a shadow root host.
+  AutoTArray<mozilla::dom::Element*, 1> mShadowHosts;
+
   // The current style scope element for selector matching.
   mozilla::dom::Element* mCurrentStyleScope;
 
@@ -396,6 +428,7 @@ struct MOZ_STACK_CLASS TreeMatchContext {
     , mHaveSpecifiedScope(false)
     , mVisitedHandling(aVisitedHandling)
     , mDocument(aDocument)
+    , mOnlyMatchHostPseudo(false)
     , mScopedRoot(nullptr)
     , mIsHTMLDocument(aDocument->IsHTMLDocument())
     , mCompatMode(aDocument->GetCompatibilityMode())
@@ -437,6 +470,7 @@ struct MOZ_STACK_CLASS ElementDependentRuleProcessorData :
     : RuleProcessorData(aPresContext, aRuleWalker)
     , mElement(aElement)
     , mTreeMatchContext(aTreeMatchContext)
+    , mElementIsFeatureless(false)
   {
     NS_ASSERTION(aElement, "null element leaked into SelectorMatches");
     NS_ASSERTION(aElement->OwnerDoc(), "Document-less node here?");
@@ -446,6 +480,7 @@ struct MOZ_STACK_CLASS ElementDependentRuleProcessorData :
   
   mozilla::dom::Element* const mElement; // weak ref, must not be null
   TreeMatchContext& mTreeMatchContext;
+  bool mElementIsFeatureless;
 };
 
 struct MOZ_STACK_CLASS ElementRuleProcessorData :
diff --git a/layout/style/nsStyleSet.cpp b/layout/style/nsStyleSet.cpp
index 5890100eb..edf61d2f9 100644
--- a/layout/style/nsStyleSet.cpp
+++ b/layout/style/nsStyleSet.cpp
@@ -1311,8 +1311,9 @@ nsStyleSet::WalkRuleProcessors(nsIStyleRuleProcessor::EnumFunc aFunc,
   if (mBindingManager) {
     // We can supply additional document-level sheets that should be walked.
     if (aWalkAllXBLStylesheets) {
-      mBindingManager->WalkAllRules(aFunc, aData);
+      mBindingManager->WalkAllRules(aFunc, aData, false);
     } else {
+      mBindingManager->WalkAllShadowRootHostRules(aFunc, aData);	    
       mBindingManager->WalkRules(aFunc, aData, &cutOffInheritance);
     }
   }