Do not create proxy hosts in the subtree of navigating frame.

content/browser/frame_host/render_frame_host_manager.cc

Index: content/browser/frame_host/render_frame_host_manager.cc
diff --git a/content/browser/frame_host/render_frame_host_manager.cc b/content/browser/frame_host/render_frame_host_manager.cc
index 0d95e1e361c7f630c4187a8eec3a49fa0828b8a0..77cdb4d3090daa66f9bb1aa0f2c8a8ace2122dc6 100644
--- a/content/browser/frame_host/render_frame_host_manager.cc
+++ b/content/browser/frame_host/render_frame_host_manager.cc
@@ -1357,8 +1357,17 @@ void RenderFrameHostManager::CommitPending() {
           linked_ptr<RenderFrameHostImpl>(old_render_frame_host.release());
     }
   } else {
-    CHECK(proxy_hosts_.find(render_frame_host_->GetSiteInstance()->GetId()) ==
-          proxy_hosts_.end());
+    if (CommandLine::ForCurrentProcess()->HasSwitch(
+        switches::kSitePerProcess) && !is_main_frame) {

[awong, 2014/09/03 21:58:38]

Document why we care that it's not a mainframe?

[nasko, 2014/09/03 23:50:19]

Done.

+      // In --site-per-process, delete the proxy for the SiteInstance we are
+      // committing
+      RenderFrameProxyHostMap::iterator iter =
+          proxy_hosts_.find(render_frame_host_->GetSiteInstance()->GetId());
+      if (iter != proxy_hosts_.end()) {
+        delete iter->second;
+        proxy_hosts_.erase(iter);
+      }
+    }
 
     // Capture the active view count on the old RFH SiteInstance, since the
     // ownership might be passed into the proxy and the pointer will be
@@ -1393,6 +1402,8 @@ void RenderFrameHostManager::CommitPending() {
       }
     }
   }
+  CHECK(proxy_hosts_.find(render_frame_host_->GetSiteInstance()->GetId()) ==

[awong, 2014/09/03 21:58:38]

Explain why this check is sensible?

[nasko, 2014/09/03 23:50:19]

Done.

+        proxy_hosts_.end());
 }
 
 void RenderFrameHostManager::ShutdownRenderFrameProxyHostsInSiteInstance(