Set an initial background for RenderFrameHosts during commit.

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 3ec87d36263b55afd0769088dbaf5edcc6980a7e..956a40740f7b623722ba49c635f7458186d48ac3 100644
--- a/content/browser/frame_host/render_frame_host_manager.cc
+++ b/content/browser/frame_host/render_frame_host_manager.cc
@@ -2168,6 +2168,15 @@ void RenderFrameHostManager::CommitPending() {
   // 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
@@ -2244,6 +2253,11 @@ void RenderFrameHostManager::CommitPending() {
   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).