Bug 1062732 - Avoid tracking descendants for restyling if we are force restyling the entire subtree. r=dbaron

layout/base/RestyleTracker.h

@@ -472,9 +472,14 @@ RestyleTracker::AddPendingRestyle(Element* aElement,
       RestyleData* curData;
       mPendingRestyles.Get(cur, &curData);
       NS_ASSERTION(curData, "expected to find a RestyleData for cur");
+      // If cur has an eRestyle_ForceDescendants restyle hint, then we
+      // know that we will get to all descendants.  Don't bother
+      // recording the descendant to restyle in that case.
+      if (!(curData->mRestyleHint & eRestyle_ForceDescendants)) {
         curData->mDescendants.AppendElement(aElement);
       }
     }
+  }
 
   mHaveLaterSiblingRestyles =
     mHaveLaterSiblingRestyles || (aRestyleHint & eRestyle_LaterSiblings) != 0;