Fix flakyness in NavigateRemoteFrame browsertest.

content/renderer/render_frame_proxy.cc

Index: content/renderer/render_frame_proxy.cc
diff --git a/content/renderer/render_frame_proxy.cc b/content/renderer/render_frame_proxy.cc
index 5af5f570fc8c0c946b22c1be6f96df2904087efe..2d45952c94b6e149667eaaa592ba7a6b68a4ef1e 100644
--- a/content/renderer/render_frame_proxy.cc
+++ b/content/renderer/render_frame_proxy.cc
@@ -195,6 +195,13 @@ void RenderFrameProxy::OnChildFrameProcessGone() {
 }
 
 void RenderFrameProxy::OnCompositorFrameSwapped(const IPC::Message& message) {
+  // If this WebFrame has already been detached, its parent will be null. This
+  // can happen when swapping a RemoteFrame with a LocalFrame, where this

[nasko, 2015/02/11 14:44:06]

nit: WebRemoteFrame and WebLocalFrame

+  // message may arrive after the frame was removed from the frame tree, but
+  // before the frame has been destroyed. http://crbug.com/446575.
+  if (!web_frame()->parent())
+    return;
+
   FrameMsg_CompositorFrameSwapped::Param param;
   if (!FrameMsg_CompositorFrameSwapped::Read(&message, &param))
     return;