Make the top bar semitransparent when in immersive fullscreen

ash/wm/custom_frame_view_ash.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 "ash/wm/custom_frame_view_ash.h"
 
 #include "ash/ash_switches.h"
 #include "ash/wm/caption_buttons/frame_caption_button_container_view.h"
 #include "ash/wm/caption_buttons/frame_maximize_button.h"
 #include "ash/wm/caption_buttons/frame_maximize_button_observer.h"
@@ skipping 269 matching lines @@
       header_mode,
       theme_image_id,
       0);
   header_painter_->PaintTitleBar(canvas, GetTitleFontList());
   header_painter_->PaintHeaderContentSeparator(canvas, header_mode);
 }
 
 void CustomFrameViewAsh::HeaderView::OnImmersiveRevealStarted() {
   fullscreen_visible_fraction_ = 0;
   SetPaintToLayer(true);
+  SetFillsBoundsOpaquely(false);
   parent()->Layout();
 }
 
 void CustomFrameViewAsh::HeaderView::OnImmersiveRevealEnded() {
   fullscreen_visible_fraction_ = 0;
   SetPaintToLayer(false);
   parent()->Layout();
 }
 
 void CustomFrameViewAsh::HeaderView::OnImmersiveFullscreenExited() {
@@ skipping 201 matching lines @@
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // CustomFrameViewAsh, private:
 
 int CustomFrameViewAsh::NonClientTopBorderHeight() const {
   return frame_->IsFullscreen() ? 0 : header_view_->GetPreferredHeight();
 }
 
 }  // namespace ash