OffscreenBrowserCompositorOutputSurface for Unified Desktop

ui/gfx/native_widget_types.h

 // 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.
 
 #ifndef UI_GFX_NATIVE_WIDGET_TYPES_H_
 #define UI_GFX_NATIVE_WIDGET_TYPES_H_
 
 #include "build/build_config.h"
 
 #if defined(OS_ANDROID)
@@ skipping 239 matching lines @@
   }
   PluginWindowHandle handle;
   SurfaceType transport_type;
   uint32 parent_client_id;
 };
 
 // AcceleratedWidget provides a surface to compositors to paint pixels.
 #if defined(OS_WIN)
 typedef HWND AcceleratedWidget;
 const AcceleratedWidget kNullAcceleratedWidget = NULL;
+const AcceleratedWidget kOffscreenAcceleratedWidget = nullptr;
 #elif defined(USE_X11)
 typedef unsigned long AcceleratedWidget;
 const AcceleratedWidget kNullAcceleratedWidget = 0;
+const AcceleratedWidget kOffscreenAcceleratedWidget = 1;

[piman, 2015/04/28 18:38:13]

I'm not fond of adding new magic numbers.
What's wrong with using kNullAcceleratedWidget for offscreen?

[oshima, 2015/04/28 20:39:01]

Is it safe to use it? kNullAcceleratedWidget seems to be used to indicate it's
uninitialized widget or doesn't exist, and I wasn't sure if it's safe.

https://code.google.com/p/chromium/codesearch#chromium/src/content/browser/gp...
https://code.google.com/p/chromium/codesearch#chromium/src/content/common/gpu...
https://code.google.com/p/chromium/codesearch#chromium/src/content/browser/fr...

I'm running try job now, and if this is safe, I'm happy to change.

 #elif defined(OS_IOS)
 typedef UIView* AcceleratedWidget;
 const AcceleratedWidget kNullAcceleratedWidget = 0;
+const AcceleratedWidget kOffscreenAcceleratedWidget = 0;
 #elif defined(OS_MACOSX)
 typedef NSView* AcceleratedWidget;
 const AcceleratedWidget kNullAcceleratedWidget = 0;
+const AcceleratedWidget kOffscreenAcceleratedWidget = 0;
 #elif defined(OS_ANDROID)
 typedef ANativeWindow* AcceleratedWidget;
 const AcceleratedWidget kNullAcceleratedWidget = 0;
+const AcceleratedWidget kOffscreenAcceleratedWidget = 0;
 #elif defined(USE_OZONE)
 typedef intptr_t AcceleratedWidget;
 const AcceleratedWidget kNullAcceleratedWidget = 0;
+const AcceleratedWidget kOffscreenAcceleratedWidget = -1;
 #else
 #error unknown platform
 #endif
 
 }  // namespace gfx
 
 #endif  // UI_GFX_NATIVE_WIDGET_TYPES_H_