(Concept patch) Simplify WTF::HashTable::add() return value for size and performance

Source/core/page/scrolling/ScrollingCoordinator.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 378 matching lines @@
 // Whenever we descend into a new frame, a new map will be created.
 typedef HashMap<const RenderLayer*, Vector<const Frame*> > LayerFrameMap;
 static void makeLayerChildFrameMap(const Frame* currentFrame, LayerFrameMap* map)
 {
     map->clear();
     const FrameTree& tree = currentFrame->tree();
     for (const Frame* child = tree.firstChild(); child; child = child->tree().nextSibling()) {
         const RenderLayer* containingLayer = child->ownerRenderer()->enclosingLayer();
         LayerFrameMap::iterator iter = map->find(containingLayer);
         if (iter == map->end())
-            iter = map->add(containingLayer, Vector<const Frame*>()).iterator;
-        iter->value.append(child);
+            map->add(containingLayer, Vector<const Frame*>()).iterator->value.append(child);
+        else
+            iter->value.append(child);
     }
 }
 
 static void convertLayerRectsToEnclosingCompositedLayerRecursive(
     const RenderLayer* curLayer,
     const LayerHitTestRects& layerRects,
     LayerHitTestRects& compositorRects,
     RenderGeometryMap& geometryMap,
     HashSet<const RenderLayer*>& layersWithRects,
     LayerFrameMap& layerChildFrameMap)
@@ skipping 13 matching lines @@
             }
         }
         if (!compositedLayer) {
             // Since this machinery is used only when accelerated compositing is enabled, we expect
             // that every layer should have an enclosing composited layer.
             ASSERT_NOT_REACHED();
             return;
         }
 
         LayerHitTestRects::iterator compIter = compositorRects.find(compositedLayer);
+        Vector<LayoutRect>* compIterValue;
         if (compIter == compositorRects.end())
-            compIter = compositorRects.add(compositedLayer, Vector<LayoutRect>()).iterator;
+            compIterValue = &compositorRects.add(compositedLayer, Vector<LayoutRect>()).iterator->value;
+        else
+            compIterValue = &compIter->value;
         // Transform each rect to the co-ordinate space of it's enclosing composited layer.
         for (size_t i = 0; i < layerIter->value.size(); ++i) {
             LayoutRect rect = layerIter->value[i];
             if (compositedLayer != curLayer) {
                 FloatQuad compositorQuad = geometryMap.mapToContainer(rect, compositedLayer->renderer());
                 rect = LayoutRect(compositorQuad.boundingBox());
                 // If the enclosing composited layer itself is scrolled, we have to undo the subtraction
                 // of its scroll offset since we want the offset relative to the scrolling content, not
                 // the element itself.
                 if (compositedLayer->renderer()->hasOverflowClip())
                     rect.move(compositedLayer->renderBox()->scrolledContentOffset());
             }
-            compIter->value.append(rect);
+            compIterValue->append(rect);
         }
     }
 
     // Walk child layers of interest
     for (const RenderLayer* childLayer = curLayer->firstChild(); childLayer; childLayer = childLayer->nextSibling()) {
         if (layersWithRects.contains(childLayer)) {
             geometryMap.pushMappingsToAncestor(childLayer, curLayer);
             convertLayerRectsToEnclosingCompositedLayerRecursive(childLayer, layerRects, compositorRects, geometryMap, layersWithRects, layerChildFrameMap);
             geometryMap.popMappingsToAncestor(curLayer);
         }
@@ skipping 491 matching lines @@
     bool frameIsScrollable = frameView && frameView->isScrollable();
     if (frameIsScrollable != m_wasFrameScrollable)
         return true;
 
     if (WebLayer* scrollLayer = frameView ? scrollingWebLayerForScrollableArea(frameView) : 0)
         return blink::WebSize(frameView->contentsSize()) != scrollLayer->bounds();
     return false;
 }
 
 } // namespace WebCore