Use black for resize gutter in tab fullscreen mode.

content/browser/renderer_host/render_widget_host_view_aura.cc

 // Copyright (c) 2012 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/renderer_host/render_widget_host_view_aura.h"
 
 #include <set>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 2831 matching lines @@
 // DelegatedFrameHost, public:
 
 ui::Layer* RenderWidgetHostViewAura::DelegatedFrameHostGetLayer() const {
   return window_->layer();
 }
 
 bool RenderWidgetHostViewAura::DelegatedFrameHostIsVisible() const {
   return !host_->is_hidden();
 }
 
+void RenderWidgetHostViewAura::DelegatedFrameHostOverrideGutterColor(
+    SkColor* color) const {
+  // In fullscreen mode resizing is uncommon, so it makes more sense to make
+  // the initial switch to fullscreen mode look better by using black as the

[danakj, 2016/04/25 22:17:58]

Doesn't this make a black flash if the page is white, instead of just having the
white background spread everywhere and then the content re-layouts on top of it?

+  // gutter color.
+  if (host_->delegate()->IsFullscreenForCurrentTab(host_))
+    *color = SK_ColorBLACK;
+}
+
 gfx::Size RenderWidgetHostViewAura::DelegatedFrameHostDesiredSizeInDIP() const {
   return window_->bounds().size();
 }
 
 bool RenderWidgetHostViewAura::DelegatedFrameCanCreateResizeLock() const {
 #if !defined(OS_CHROMEOS)
   // On Windows and Linux, holding pointer moves will not help throttling
   // resizes.
   // TODO(piman): on Windows we need to block (nested message loop?) the
   // WM_SIZE event. On Linux we need to throttle at the WM level using
@@ skipping 65 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewBase, public:
 
 // static
 void RenderWidgetHostViewBase::GetDefaultScreenInfo(WebScreenInfo* results) {
   GetScreenInfoForWindow(results, NULL);
 }
 
 }  // namespace content