Add app.window.alphaEnabled() and onAlphaEnabledChanged.

apps/app_window.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 "apps/app_window.h"
 
 #include <algorithm>
 
 #include "apps/app_window_geometry_cache.h"
 #include "apps/app_window_registry.h"
@@ skipping 266 matching lines @@
   // Initialize the window
   CreateParams new_params = LoadDefaults(params);
   window_type_ = new_params.window_type;
   window_key_ = new_params.window_key;
 
   // Windows cannot be always-on-top in fullscreen mode for security reasons.
   cached_always_on_top_ = new_params.always_on_top;
   if (new_params.state == ui::SHOW_STATE_FULLSCREEN)
     new_params.always_on_top = false;
 
+  requested_transparent_background_ = new_params.transparent_background;
+
   native_app_window_.reset(delegate_->CreateNativeAppWindow(this, new_params));
 
   // Prevent the browser process from shutting down while this window exists.
   AppsClient::Get()->IncrementKeepAliveCount();
   UpdateExtensionAppIcon();
   AppWindowRegistry::Get(browser_context_)->AddAppWindow(this);
 
   if (new_params.hidden) {
     // Although the window starts hidden by default, calling Hide() here
     // notifies observers of the window being hidden.
@@ skipping 438 matching lines @@
   OnNativeWindowChanged();
 }
 
 bool AppWindow::IsAlwaysOnTop() const { return cached_always_on_top_; }
 
 void AppWindow::WindowEventsReady() {
   can_send_events_ = true;
   SendOnWindowShownIfShown();
 }
 
+bool AppWindow::RequestedTransparentBackground() const {
+  return requested_transparent_background_;
+}
+
 void AppWindow::GetSerializedState(base::DictionaryValue* properties) const {
   DCHECK(properties);
 
   properties->SetBoolean("fullscreen",
                          native_app_window_->IsFullscreenOrPending());
   properties->SetBoolean("minimized", native_app_window_->IsMinimized());
   properties->SetBoolean("maximized", native_app_window_->IsMaximized());
   properties->SetBoolean("alwaysOnTop", IsAlwaysOnTop());
   properties->SetBoolean("hasFrameColor", native_app_window_->HasFrameColor());
+  properties->SetBoolean("alphaEnabled",
+                         requested_transparent_background_
+                             ? native_app_window_->CanHaveAlphaEnabled()
+                             : false);

[Wez, 2014/07/11 17:14:10]

nit: Or simply |requested_transparent_background_ &&
native_app_window_->CanHaveAlphaEnabled()| ?

[jackhou1, 2014/07/14 03:05:24]

Done.

 
   // These properties are undocumented and are to enable testing. Alpha is
   // removed to
   // make the values easier to check.
   SkColor transparent_white = ~SK_ColorBLACK;
   properties->SetInteger(
       "activeFrameColor",
       native_app_window_->ActiveFrameColor() & transparent_white);
   properties->SetInteger(
       "inactiveFrameColor",
@@ skipping 378 matching lines @@
         region.bounds.x(),
         region.bounds.y(),
         region.bounds.right(),
         region.bounds.bottom(),
         region.draggable ? SkRegion::kUnion_Op : SkRegion::kDifference_Op);
   }
   return sk_region;
 }
 
 }  // namespace apps