Issue mcp-graveyard/UXP#1219 - Align computed DOM styles with mainstream behvior.

This updates our behavior for computed DOM styling to no longer return
null on elements that have no display, but return a 0-length (empty)
style instead and don't throw. For this we stop looking at having a
presentation for the style and just look at the document instead.

This resolves #1219

2 files changed, 3 insertions, 32 deletions

diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index 1288b34353..47b46dda06 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -10950,35 +10950,12 @@ nsGlobalWindow::GetComputedStyleHelperOuter(Element& aElt,
 {
   MOZ_RELEASE_ASSERT(IsOuterWindow());
 
-  if (!mDocShell) {
+  if (!mDoc) {
     return nullptr;
   }
 
-  nsCOMPtr<nsIPresShell> presShell = mDocShell->GetPresShell();
-
-  if (!presShell) {
-    // Try flushing frames on our parent in case there's a pending
-    // style change that will create the presshell.
-    auto* parent = nsGlobalWindow::Cast(GetPrivateParent());
-    if (!parent) {
-      return nullptr;
-    }
-
-    parent->FlushPendingNotifications(Flush_Frames);
-
-    // Might have killed mDocShell
-    if (!mDocShell) {
-      return nullptr;
-    }
-
-    presShell = mDocShell->GetPresShell();
-    if (!presShell) {
-      return nullptr;
-    }
-  }
-
   RefPtr<nsComputedDOMStyle> compStyle =
-    NS_NewComputedDOMStyle(&aElt, aPseudoElt, presShell,
+    NS_NewComputedDOMStyle(&aElt, aPseudoElt, mDoc,
                            aDefaultStylesOnly ? nsComputedDOMStyle::eDefaultOnly :
                                                 nsComputedDOMStyle::eAll);
 
diff --git a/dom/smil/nsSMILCSSProperty.cpp b/dom/smil/nsSMILCSSProperty.cpp
index 53f3e0fbf7..e745124432 100644
--- a/dom/smil/nsSMILCSSProperty.cpp
+++ b/dom/smil/nsSMILCSSProperty.cpp
@@ -38,14 +38,8 @@ GetCSSComputedValue(Element* aElem,
     return false;
   }
 
-  nsIPresShell* shell = doc->GetShell();
-  if (!shell) {
-    NS_WARNING("Unable to look up computed style -- no pres shell");
-    return false;
-  }
-
   RefPtr<nsComputedDOMStyle> computedStyle =
-    NS_NewComputedDOMStyle(aElem, EmptyString(), shell);
+    NS_NewComputedDOMStyle(aElem, EmptyString(), doc);
 
   computedStyle->GetPropertyValue(aPropID, aResult);
   return true;