Always create FrameTreeNodes and RenderFrameHosts for every frame.

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index b21d9e047b9a4e914326cd43acb012f2db1e9439..e2a406ee54ce3168b733506e9fcd6a9dc2823802 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -955,11 +955,11 @@ void RenderViewImpl::Initialize(RenderViewImplParams* params) {
 
   ApplyWebPreferences(webkit_preferences_, webview());
 
-  main_render_frame_.reset(
-      RenderFrameImpl::Create(this, params->main_frame_routing_id));
+  main_render_frame_ =
+      RenderFrameImpl::Create(this, params->main_frame_routing_id);
   // The main frame WebFrame object is closed by
   // RenderViewImpl::frameDetached().
-  webview()->setMainFrame(WebFrame::create(main_render_frame_.get()));
+  webview()->setMainFrame(WebFrame::create(main_render_frame_));
 
   if (switches::IsTouchDragDropEnabled())
     webview()->settings()->setTouchDragDropEnabled(true);
@@ -2555,7 +2555,7 @@ bool RenderViewImpl::enumerateChosenDirectory(
 
 void RenderViewImpl::initializeHelperPluginWebFrame(
     blink::WebHelperPlugin* plugin) {
-  plugin->initializeFrame(main_render_frame_.get());
+  plugin->initializeFrame(main_render_frame_);
 }
 
 void RenderViewImpl::didStartLoading() {
@@ -3167,6 +3167,12 @@ void RenderViewImpl::didDisownOpener(blink::WebFrame* frame) {
 }
 
 void RenderViewImpl::frameDetached(WebFrame* frame) {
+  if (!frame->parent()) {
+    // We cannot rely on our main_render_frame_ anymore.  It will be deleted as
+    // part of RenderFrameImpl::frameDetached.  We expect to be deleted
+    // right away, but we clear this out to be safe.
+    main_render_frame_ = NULL;

[Charlie Reis, 2013/11/21 23:59:15]

I added this as well, since I didn't like the idea of leaving main_render_frame_
as garbage when it gets detached.

(It doesn't appear that RenderViewImpl gets deleted in the same task on the
message loop, but perhaps there's some guarantee it will be the next task? 
Otherwise we'd have lots of problems when accessing webview(), etc. after this
point.)

+  }
   FOR_EACH_OBSERVER(RenderViewObserver, observers_, FrameDetached(frame));
 }