Band-aid fix for bug 487406

content/browser/frame_host/render_frame_proxy_host.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/frame_host/render_frame_proxy_host.h"
 
 #include "base/lazy_instance.h"
 #include "content/browser/bad_message.h"
 #include "content/browser/frame_host/cross_process_frame_connector.h"
 #include "content/browser/frame_host/frame_tree.h"
@@ skipping 81 matching lines @@
       static_cast<RenderWidgetHostViewChildFrame*>(view));
 }
 
 RenderViewHostImpl* RenderFrameProxyHost::GetRenderViewHost() {
   return frame_tree_node_->frame_tree()->GetRenderViewHost(
       site_instance_.get());
 }
 
 void RenderFrameProxyHost::TakeFrameHostOwnership(
     scoped_ptr<RenderFrameHostImpl> render_frame_host) {
+  CHECK(render_frame_host_ == nullptr);

[nasko, 2015/05/14 14:09:01]

CHECK_EQ?

[ncarter (slow), 2015/05/14 17:16:13]

Tried five things:

CHECK(render_frame_host_ == nullptr);  // Compiles
CHECK_EQ(render_frame_host_, nullptr);  // Doesn't compile
CHECK_EQ(render_frame_host_.get(), nullptr);  // Doesn't compile either
CHECK_EQ(render_frame_host_, static_cast<RenderFrameHost*>(nullptr));  // Still
doesn't compile.
CHECK_EQ(render_frame_host_.get(), static_cast<RenderFrameHost*>(nullptr));  //
Compiles! But at what cost?

There are some (but not many) examples of option 5 in the codebase:
https://code.google.com/p/chromium/codesearch#search/&q=CHECK_EQ.*nullptr&sq=...

I think the version with operator== is easiest on the eyes. CHECK_EQ(ptr1, ptr2)
is a good idea if you have two pointers variables that you expect to be equal,
because then stdout will show you which of the mismatched address values is null
or not. But if you're testing the value of a single pointer value against
nullity, I don't think it helps much to see the particular non-null address on
stdout.

   render_frame_host_ = render_frame_host.Pass();
   render_frame_host_->set_render_frame_proxy_host(this);
 }
 
 scoped_ptr<RenderFrameHostImpl> RenderFrameProxyHost::PassFrameHostOwnership() {
   render_frame_host_->set_render_frame_proxy_host(NULL);
   return render_frame_host_.Pass();
 }
 
 bool RenderFrameProxyHost::Send(IPC::Message *msg) {
@@ skipping 144 matching lines @@
         base::Bind(&MessagePortMessageFilter::RouteMessageEventWithMessagePorts,
                    message_port_message_filter, target_rfh->GetRoutingID(),
                    new_params));
   } else {
     target_rfh->Send(
         new FrameMsg_PostMessageEvent(target_rfh->GetRoutingID(), new_params));
   }
 }
 
 }  // namespace content