Add a trace for RenderLayer::updateLayerPositionsAfterLayout.

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 218 matching lines @@
     }
     ASSERT(rootLayer == root());
 
     LayoutPoint offset;
     parent()->convertToLayerCoords(rootLayer, offset);
     return offset;
 }
 
 void RenderLayer::updateLayerPositionsAfterLayout(const RenderLayer* rootLayer, UpdateLayerPositionsFlags flags)
 {
+    TRACE_EVENT0("blink_rendering", "RenderLayer::updateLayerPositionsAfterLayout");
     RenderGeometryMap geometryMap(UseTransforms);
     if (this != rootLayer)
         geometryMap.pushMappingsToAncestor(parent(), 0);
     updateLayerPositions(&geometryMap, flags);
 }
 
 void RenderLayer::updateLayerPositions(RenderGeometryMap* geometryMap, UpdateLayerPositionsFlags flags)
 {
     updateLayerPosition(); // For relpositioned layers or non-positioned layers,
                            // we need to keep in sync, since we may have shifted relative
@@ skipping 3686 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif