Give the main frame a RenderWidget.

content/browser/frame_host/render_frame_host_manager.cc

 // Copyright 2013 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_host_manager.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/command_line.h"
@@ skipping 235 matching lines @@
   ResetProxyHosts();
 
   // Release the WebUI prior to resetting the current RenderFrameHost, as the
   // WebUI accesses the RenderFrameHost during cleanup.
   web_ui_.reset();
 
   // We should always have a current RenderFrameHost except in some tests.
   SetRenderFrameHost(scoped_ptr<RenderFrameHostImpl>());
 }
 
-void RenderFrameHostManager::Init(BrowserContext* browser_context,
-                                  SiteInstance* site_instance,
+void RenderFrameHostManager::Init(SiteInstance* site_instance,
                                   int32 view_routing_id,
                                   int32 frame_routing_id,
                                   int32 widget_routing_id) {
-  // Create a RenderViewHost and RenderFrameHost, once we have an instance.  It
-  // is important to immediately give this SiteInstance to a RenderViewHost so
-  // that the SiteInstance is ref counted.
-  if (!site_instance)
-    site_instance = SiteInstance::Create(browser_context);
-
+  DCHECK(site_instance);
+  // TODO(avi): While RenderViewHostImpl is-a RenderWidgetHostImpl, this must
+  // hold true to avoid having two RenderWidgetHosts for the top-level frame.
+  // https://crbug.com/545684
+  DCHECK_IMPLIES(frame_tree_node_->IsMainFrame(),
+                 view_routing_id == widget_routing_id);
   int flags = delegate_->IsHidden() ? CREATE_RF_HIDDEN : 0;
   SetRenderFrameHost(CreateRenderFrameHost(site_instance, view_routing_id,
                                            frame_routing_id, widget_routing_id,
                                            flags));
 
   // Notify the delegate of the creation of the current RenderFrameHost.
   // Do this only for subframes, as the main frame case is taken care of by
   // WebContentsImpl::Init.
   if (!frame_tree_node_->IsMainFrame()) {
     delegate_->NotifySwappedFromRenderManager(
@@ skipping 1414 matching lines @@
 
   bool swapped_out = !!(flags & CREATE_RF_SWAPPED_OUT);
   bool hidden = !!(flags & CREATE_RF_HIDDEN);
 
   // Create a RVH for main frames, or find the existing one for subframes.
   FrameTree* frame_tree = frame_tree_node_->frame_tree();
   RenderViewHostImpl* render_view_host = nullptr;
   if (frame_tree_node_->IsMainFrame()) {
     render_view_host = frame_tree->CreateRenderViewHost(
         site_instance, view_routing_id, frame_routing_id, swapped_out, hidden);
+    // TODO(avi): It's a bit bizarre that this logic lives here instead of in
+    // CreateRenderFrame(). It turns out that FrameTree::CreateRenderViewHost
+    // doesn't /always/ create a new RenderViewHost. It first tries to find an
+    // already existing one to reuse by a SiteInstance lookup. If it finds one,
+    // then the supplied routing IDs are completely ignored.
+    // CreateRenderFrame() could do this lookup too, but it seems redundant to

[ncarter (slow), 2015/10/26 22:27:42]

Agree, gross to do the lookup in two places (since it's actually implemented as
a lookup with garbage collection, super gross to duplicate that).

+    // do this lookup in two places. This is a good yak shave to clean up, or,
+    // if just ignored, should be an easy cleanup once RenderViewHostImpl has-a
+    // RenderWidgetHostImpl. https://crbug.com/545684
+    if (view_routing_id == MSG_ROUTING_NONE) {
+      widget_routing_id = render_view_host->GetRoutingID();
+    } else {
+      DCHECK_EQ(view_routing_id, render_view_host->GetRoutingID());

[ncarter (slow), 2015/10/26 22:27:43]

Wow. I see why this is safe but it's darn subtle. OK.

+    }
   } else {
     render_view_host = frame_tree->GetRenderViewHost(site_instance);
     CHECK(render_view_host);
   }
 
   return RenderFrameHostFactory::Create(
       site_instance, render_view_host, render_frame_delegate_,
       render_widget_delegate_, frame_tree, frame_tree_node_, frame_routing_id,
       widget_routing_id, flags);
 }
@@ skipping 937 matching lines @@
 int RenderFrameHostManager::GetOpenerRoutingID(SiteInstance* instance) {
   if (!frame_tree_node_->opener())
     return MSG_ROUTING_NONE;
 
   return frame_tree_node_->opener()
       ->render_manager()
       ->GetRoutingIdForSiteInstance(instance);
 }
 
 }  // namespace content