Set an initial background for RenderFrameHosts during commit.

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 <stddef.h>
 
 #include <algorithm>
 #include <string>
@@ skipping 2150 matching lines @@
   } else {
     // PlzNavigate
     DCHECK(speculative_render_frame_host_);
     old_render_frame_host =
         SetRenderFrameHost(std::move(speculative_render_frame_host_));
   }
 
   // The process will no longer try to exit, so we can decrement the count.
   render_frame_host_->GetProcess()->RemovePendingView();
 
+  // Save off the old background color before possibly deleting the
+  // old RenderWidgetHostView.
+  SkColor old_background_color = SK_ColorWHITE;
+  bool has_old_background_color = false;
+  if (old_render_frame_host && old_render_frame_host->GetView()) {

[nasko, 2017/03/08 22:54:20]

Why null check old_render_frame_host? It is set unconditionally above and used
without checking for nullness further down.

[chrishtr, 2017/03/08 23:02:59]

Done.

+    has_old_background_color = true;
+    old_background_color = old_render_frame_host->GetView()->background_color();
+  }
+
   // The RenderViewHost keeps track of the main RenderFrameHost routing id.
   // If this is committing a main frame navigation, update it and set the
   // routing id in the RenderViewHost associated with the old RenderFrameHost
   // to MSG_ROUTING_NONE.
   if (is_main_frame) {
     RenderViewHostImpl* rvh = render_frame_host_->render_view_host();
     rvh->set_main_frame_routing_id(render_frame_host_->routing_id());
 
     // If we are reusing the RenderViewHost, we need to create the
     // RenderWidgetHostView if this is the main frame.
@@ skipping 56 matching lines @@
       frame_tree_node_->frame_tree()->SetPageFocus(
           render_frame_host_->GetSiteInstance(), true);
     }
   }
 
   // Notify that we've swapped RenderFrameHosts. We do this before shutting down
   // the RFH so that we can clean up RendererResources related to the RFH first.
   delegate_->NotifySwappedFromRenderManager(
       old_render_frame_host.get(), render_frame_host_.get(), is_main_frame);
 
+  if (has_old_background_color) {
+    delegate_->NotifyInitialBackground(old_background_color,

[nasko, 2017/03/08 22:54:20]

Is there any specific reason to go through the delegate interface? This class
manages both the old and the new RFH, so it can just tell the new RFH directly
what the background color is.

[chrishtr, 2017/03/08 23:02:59]

Just thought it might be cleaner. I'm happy to inline if you think that;s
better.

+                                       render_frame_host_.get());
+  }
+
   // Swap out the old frame now that the new one is visible.
   // This will swap it out and schedule it for deletion when the swap out ack
   // arrives (or immediately if the process isn't live).
   SwapOutOldFrame(std::move(old_render_frame_host));
 
   // Since the new RenderFrameHost is now committed, there must be no proxies
   // for its SiteInstance. Delete any existing ones.
   DeleteRenderFrameProxyHost(render_frame_host_->GetSiteInstance());
 
   // If this is a subframe, it should have a CrossProcessFrameConnector
@@ skipping 518 matching lines @@
                                              resolved_url)) {
     DCHECK(!dest_instance ||
            dest_instance == render_frame_host_->GetSiteInstance());
     return false;
   }
 
   return true;
 }
 
 }  // namespace content