Fix swapbuffers callback crash

chrome/renderer/webgraphicscontext3d_command_buffer_impl.cc

Index: chrome/renderer/webgraphicscontext3d_command_buffer_impl.cc
diff --git a/chrome/renderer/webgraphicscontext3d_command_buffer_impl.cc b/chrome/renderer/webgraphicscontext3d_command_buffer_impl.cc
index 1be54610cbf89ce6ffa1b5915bfd5aa91d452152..c6c4b5b0e73d4d05a4aeb4f8c412acf6d8413b49 100644
--- a/chrome/renderer/webgraphicscontext3d_command_buffer_impl.cc
+++ b/chrome/renderer/webgraphicscontext3d_command_buffer_impl.cc
@@ -119,7 +119,8 @@ bool WebGraphicsContext3DCommandBufferImpl::initialize(
     if (context_) {
       ggl::SetSwapBuffersCallback(
           context_,
-          NewCallback(renderview, &RenderView::DidFlushPaint));
+          NewCallback(this,
+                      &WebGraphicsContext3DCommandBufferImpl::OnSwapBuffers));
     }
   } else {
     bool compositing_enabled = !CommandLine::ForCurrentProcess()->HasSwitch(
@@ -1033,4 +1034,12 @@ void WebGraphicsContext3DCommandBufferImpl::copyTextureToCompositor(
   glFlush();
 }
 
+void WebGraphicsContext3DCommandBufferImpl::OnSwapBuffers() {
+  // This may be called after tear-down of the RenderView.
+  RenderView* renderview =
+      web_view_ ? RenderView::FromWebView(web_view_) : NULL;
+  if (renderview)
+    renderview->DidFlushPaint();
+}
+
 #endif  // defined(ENABLE_GPU)