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

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 3873 matching lines @@
         Vector<LayoutRect> rect;
 
         if (renderBox() && renderBox()->scrollsOverflow()) {
             // For scrolling layers, rects are taken to be in the space of the contents.
             // We need to include both the entire contents, and also the bounding box
             // of the layer in the space of it's parent (eg. for border / scroll bars).
             rect.append(m_scrollableArea->overflowRect());
             rects.set(this, rect);
             if (const RenderLayer* parentLayer = parent()) {
                 LayerHitTestRects::iterator iter = rects.find(parentLayer);
-                if (iter == rects.end())
-                    iter = rects.add(parentLayer, Vector<LayoutRect>()).iterator;
-                iter->value.append(boundingBox(parentLayer));
+                if (iter == rects.end()) {
+                    rects.add(parentLayer, Vector<LayoutRect>()).iterator->value.append(boundingBox(parentLayer));
+                } else {
+                    iter->value.append(boundingBox(parentLayer));
+                }
             }
         } else {
             rect.append(localBoundingBox());
             rects.set(this, rect);
         }
     }
 
     for (RenderLayer* child = firstChild(); child; child = child->nextSibling())
         child->addLayerHitTestRects(rects);
 }
@@ skipping 12 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif