Add support for transparent background API

chrome/browser/ui/views/apps/chrome_native_app_window_views.cc

 // Copyright 2014 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/apps/chrome_native_app_window_views.h"
 
 #include "apps/ui/views/app_window_frame_view.h"
 #include "base/command_line.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/browser/app_mode/app_mode_utils.h"
@@ skipping 196 matching lines @@
   std::string app_name = web_app::GenerateApplicationNameFromExtensionId(
       app_window()->extension_id());
 
   views::Widget::InitParams init_params(views::Widget::InitParams::TYPE_WINDOW);
   init_params.delegate = this;
   init_params.remove_standard_frame = IsFrameless() || has_frame_color_;
   init_params.use_system_default_icon = true;
   // TODO(erg): Conceptually, these are toplevel windows, but we theoretically
   // could plumb context through to here in some cases.
   init_params.top_level = true;
-  if (create_params.transparent_background)
+  if (create_params.alpha_enabled)
     init_params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
   init_params.keep_on_top = create_params.always_on_top;
 
 #if defined(OS_LINUX) && !defined(OS_CHROMEOS)
   // Set up a custom WM_CLASS for app windows. This allows task switchers in
   // X11 environments to distinguish them from main browser windows.
   init_params.wm_class_name = web_app::GetWMClassFromAppName(app_name);
   init_params.wm_class_class = ShellIntegrationLinux::GetProgramClassName();
   const char kX11WindowRoleApp[] = "app";
   init_params.wm_role_name = std::string(kX11WindowRoleApp);
@@ skipping 468 matching lines @@
     InitializePanelWindow(create_params);
   } else {
     InitializeDefaultWindow(create_params);
   }
   extension_keybinding_registry_.reset(new ExtensionKeybindingRegistryViews(
       Profile::FromBrowserContext(app_window->browser_context()),
       widget()->GetFocusManager(),
       extensions::ExtensionKeybindingRegistry::PLATFORM_APPS_ONLY,
       NULL));
 }