Fix swapbuffers callback crash

chrome/renderer/webgraphicscontext3d_command_buffer_impl.h

Index: chrome/renderer/webgraphicscontext3d_command_buffer_impl.h
diff --git a/chrome/renderer/webgraphicscontext3d_command_buffer_impl.h b/chrome/renderer/webgraphicscontext3d_command_buffer_impl.h
index b4f99d2f264e88ff3b64531d18ff23e86a512433..2b20bbf861c73e24b2b11e7c14b5a7d19217e82e 100644
--- a/chrome/renderer/webgraphicscontext3d_command_buffer_impl.h
+++ b/chrome/renderer/webgraphicscontext3d_command_buffer_impl.h
@@ -372,6 +372,9 @@ class WebGraphicsContext3DCommandBufferImpl
   ggl::Context* context() { return context_; }
 
  private:
+  // SwapBuffers callback;
+  void OnSwapBuffers();
+
   // The GGL context we use for OpenGL rendering.
   ggl::Context* context_;
   // If rendering directly to WebView, weak pointer to it.