Track scissored damage area for WebGL

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 168 matching lines @@
     return renderer()->debugName();
 }
 
 RenderLayerCompositor* RenderLayer::compositor() const
 {
     if (!renderer()->view())
         return 0;
     return renderer()->view()->compositor();
 }
 
-void RenderLayer::contentChanged(ContentChangeType changeType)
+void RenderLayer::contentChanged(ContentChangeType changeType, const IntRect& dirtyRect)
 {
     // updateLayerCompositingState will query compositingReasons for accelerated overflow scrolling.
     // This is tripped by LayoutTests/compositing/content-changed-chicken-egg.html
     DisableCompositingQueryAsserts disabler;
 
     if (changeType == CanvasChanged)
         compositor()->setNeedsCompositingUpdate(CompositingUpdateAfterCompositingInputChange);
 
     if (changeType == CanvasContextChanged) {
         compositor()->setNeedsCompositingUpdate(CompositingUpdateAfterCompositingInputChange);
 
         // Although we're missing test coverage, we need to call
         // GraphicsLayer::setContentsToPlatformLayer with the new platform
         // layer for this canvas.
         // See http://crbug.com/349195
         if (hasCompositedLayerMapping())
             compositedLayerMapping()->setNeedsGraphicsLayerUpdate(GraphicsLayerUpdateSubtree);
     }
 
     if (m_compositedLayerMapping)
-        m_compositedLayerMapping->contentChanged(changeType);
+        m_compositedLayerMapping->contentChanged(changeType, dirtyRect);
 }
 
 bool RenderLayer::paintsWithFilters() const
 {
     if (!renderer()->hasFilter())
         return false;
 
     // https://code.google.com/p/chromium/issues/detail?id=343759
     DisableCompositingQueryAsserts disabler;
     return !m_compositedLayerMapping || compositingState() != PaintsIntoOwnBacking;
@@ skipping 2625 matching lines @@
     }
 }
 
 void showLayerTree(const blink::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif