Always delete the old content array so that we run destructors. b=397022 r+sr=bzbarsky a=roc

layout/style/nsStyleStruct.cpp

@@ -1402,7 +1402,11 @@ nsChangeHint nsStyleContent::MaxDifference()
 
 nsresult nsStyleContent::AllocateContents(PRUint32 aCount)
 {
-  if (aCount != mContentCount) {
+  // We need to run the destructors of the elements of mContents, so we
+  // delete and reallocate even if aCount == mContentCount.  (If
+  // nsStyleContentData had its members private and managed their
+  // ownership on setting, we wouldn't need this, but that seems
+  // unnecessary at this point.)
   DELETE_ARRAY_IF(mContents);
   if (aCount) {
     mContents = new nsStyleContentData[aCount];
@@ -1412,7 +1416,6 @@ nsresult nsStyleContent::AllocateContents(PRUint32 aCount)
     }
   }
   mContentCount = aCount;
-  }
   return NS_OK;
 }