If a GraphicsLayerChromium goes away during the middle of paint, its

Source/WebCore/platform/graphics/chromium/LayerRendererChromium.cpp

 /*
  * Copyright (C) 2010 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 545 matching lines @@
     GLC(m_context.get(), m_context->blendFunc(GraphicsContext3D::ONE, GraphicsContext3D::ONE_MINUS_SRC_ALPHA));
     GLC(m_context.get(), m_context->enable(GraphicsContext3D::SCISSOR_TEST));
 
     // Update the contents of the render surfaces. We traverse the array from
     // back to front to guarantee that nested render surfaces get rendered in the
     // correct order.
     for (int surfaceIndex = renderSurfaceLayerList.size() - 1; surfaceIndex >= 0 ; --surfaceIndex) {
         CCLayerImpl* renderSurfaceLayer = renderSurfaceLayerList[surfaceIndex].get();
         RenderSurfaceChromium* renderSurface = renderSurfaceLayer->renderSurface();
         ASSERT(renderSurface);
+        if (!renderSurface)
+            continue;
 
         renderSurface->setSkipsDraw(true);
 
         // Render surfaces whose drawable area has zero width or height
         // will have no layers associated with them and should be skipped.
         if (!renderSurface->layerList().size())
             continue;
 
         // Skip completely transparent render surfaces.
         if (!renderSurface->drawOpacity())
@@ skipping 381 matching lines @@
     if (layer->preserves3D() && (!layer->parent() || !layer->parent()->preserves3D()))
         m_layerSorter.sort(&descendants.at(thisLayerIndex), descendants.end());
 }
 
 void LayerRendererChromium::updateCompositorResources(const LayerList& renderSurfaceLayerList)
 {
     for (int surfaceIndex = renderSurfaceLayerList.size() - 1; surfaceIndex >= 0 ; --surfaceIndex) {
         CCLayerImpl* renderSurfaceLayer = renderSurfaceLayerList[surfaceIndex].get();
         RenderSurfaceChromium* renderSurface = renderSurfaceLayer->renderSurface();
         ASSERT(renderSurface);
+        if (!renderSurface)
+            continue;
 
         if (!renderSurface->layerList().size() || !renderSurface->drawOpacity())
             continue;
 
         const LayerList& layerList = renderSurface->layerList();
         ASSERT(layerList.size());
         for (unsigned layerIndex = 0; layerIndex < layerList.size(); ++layerIndex) {
             CCLayerImpl* ccLayerImpl = layerList[layerIndex].get();
+            if (!ccLayerImpl)

[nduca, 2011/09/09 23:24:09]

(drive by) How do we prevent this crap from happening in the future? It seems to
me that rendersurfaces are crazy fragile as implemented.

+                continue;
             if (ccLayerImpl->renderSurface() && ccLayerImpl->renderSurface() != renderSurface)
                 continue;
 
             updateCompositorResources(ccLayerImpl);
         }
     }
 }
 
 void LayerRendererChromium::updateCompositorResources(CCLayerImpl* ccLayerImpl)
 {
@@ skipping 75 matching lines @@
         return false;
     }
 #endif
 
     setDrawViewportRect(renderSurface->contentRect(), false);
     return true;
 }
 
 void LayerRendererChromium::drawLayer(CCLayerImpl* layer, RenderSurfaceChromium* targetSurface)
 {
+    if (!layer)
+        return;
+
     if (layer->renderSurface() && layer->renderSurface() != targetSurface) {
         layer->renderSurface()->draw(layer->getDrawRect());
         layer->renderSurface()->releaseContentsTexture();
         return;
     }
 
     if (!layer->drawsContent())
         return;
 
     if (!layer->opacity())
@@ skipping 405 matching lines @@
 PassOwnPtr<CCLayerTreeHostImplProxy> LayerRendererChromium::createLayerTreeHostImplProxy()
 {
     OwnPtr<CCLayerTreeHostImplProxy> proxy = LayerRendererChromiumImplProxy::create(this);
     proxy->start();
     return proxy.release();
 }
 
 } // namespace WebCore
 
 #endif // USE(ACCELERATED_COMPOSITING)