Ensure that modal dialogs from subframes can be cleaned up correctly.

content/browser/renderer_host/render_view_host_impl.cc

Index: content/browser/renderer_host/render_view_host_impl.cc
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index a8cf4ea17b204e3d258b9900936755ac08d41a6a..f83d1eecc815413ede8210b08e2df069097b17f5 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -1177,7 +1177,9 @@ void RenderViewHostImpl::OnRenderProcessGone(int status, int exit_code) {
   render_view_termination_status_ =
       static_cast<base::TerminationStatus>(status);
 
-  // Reset frame tree state associated with this process.
+  // Reset frame tree state associated with this process.  This must happen
+  // before RenderViewTerminated because observers expect the subframes of any
+  // affected frames to be cleared first.
   delegate_->GetFrameTree()->RenderProcessGone(this);
 
   // Our base class RenderWidgetHost needs to reset some stuff.