Make the top bar semitransparent when in immersive fullscreen

chrome/browser/ui/views/frame/immersive_mode_controller_ash.cc

 // Copyright 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 "chrome/browser/ui/views/frame/immersive_mode_controller_ash.h"
 
 #include "ash/shell.h"
 #include "ash/wm/window_state.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/ui/fullscreen/fullscreen_controller.h"
@@ skipping 150 matching lines @@
   if (show_tab_indicators != browser_view_->tabstrip()->IsImmersiveStyle()) {
     browser_view_->tabstrip()->SetImmersiveStyle(show_tab_indicators);
     return true;
   }
   return false;
 }
 
 void ImmersiveModeControllerAsh::OnImmersiveRevealStarted() {
   visible_fraction_ = 0;
   browser_view_->top_container()->SetPaintToLayer(true);
+  browser_view_->top_container()->SetFillsBoundsOpaquely(false);

[James Cook, 2014/02/24 17:40:07]

So the top container for *all* immersive fullscreen reveals is now going to be
transparent?  Does that look OK for the typical browser window case with opaque
tabs?

[pkotwicz, 2014/02/27 19:26:51]

This merely disables some of the optimizations that we do if the contents of a
layer are fully opaque. This does not actually set the opacity of a layer.
Immersive reveals for browser windows will look exactly the same because because
we use fully opaque image assets to paint the top container.

   UpdateTabIndicators();
   LayoutBrowserRootView();
   FOR_EACH_OBSERVER(Observer, observers_, OnImmersiveRevealStarted());
 }
 
 void ImmersiveModeControllerAsh::OnImmersiveRevealEnded() {
   visible_fraction_ = 0;
   browser_view_->top_container()->SetPaintToLayer(false);
   UpdateTabIndicators();
   LayoutBrowserRootView();
@@ skipping 60 matching lines @@
   // prevent it from being revealed.
   bool in_tab_fullscreen = content::Source<FullscreenController>(source)->
       IsFullscreenForTabOrPending();
   ash::wm::GetWindowState(native_window_)->set_hide_shelf_when_fullscreen(
       in_tab_fullscreen);
   ash::Shell::GetInstance()->UpdateShelfVisibility();
 
   if (tab_indicator_visibility_changed)
     LayoutBrowserRootView();
 }