Remove unnecessary setNeedsCompositingUpdate(CompositingUpdateRebuildTree)

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 1243 matching lines @@
         beforeChild->setPreviousSibling(child);
         child->setNextSibling(beforeChild);
         ASSERT(beforeChild != child);
     } else
         setLastChild(child);
 
     child->m_parent = this;
 
     setNeedsCompositingInputsUpdate();
 
-    // FIXME: Why do we need to explicitly set CompositingUpdateRebuildTree?
-    compositor()->setNeedsCompositingUpdate(CompositingUpdateRebuildTree);
-
     if (child->stackingNode()->isNormalFlowOnly())
         m_stackingNode->dirtyNormalFlowList();
 
     if (!child->stackingNode()->isNormalFlowOnly() || child->firstChild()) {
         // Dirty the z-order list in which we are contained. The ancestorStackingContextNode() can be null in the
         // case where we're building up generated content layers. This is ok, since the lists will start
         // off dirty in that case anyway.
         child->stackingNode()->dirtyStackingContextZOrderLists();
     }
 
@@ skipping 2468 matching lines @@
     }
 }
 
 void showLayerTree(const blink::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif