Uses copy request to flatten the layers to do screen rotation animation.

chrome/browser/flag_descriptions.h

 // Copyright 2017 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 CHROME_BROWSER_FLAG_DESCRIPTIONS_H_
 #define CHROME_BROWSER_FLAG_DESCRIPTIONS_H_
 
 // Includes needed for macros allowing conditional compilation of some strings.
 #include "build/build_config.h"
 #include "build/buildflag.h"
@@ skipping 768 matching lines @@
 // Description for the flag which can be used for support for javascript locking
 // rotation
 extern const char kAshScreenOrientationLockDescription[];
 
 // Title for the flag to enable the mirrored screen mode.
 extern const char kAshEnableMirroredScreenName[];
 
 // Description for the flag to enable the mirrored screen mode.
 extern const char kAshEnableMirroredScreenDescription[];
 
+// Title for the flag to enable smooth rotation animations.

[oshima, 2017/03/31 00:14:34]

can you file a bug to cleanup the flag and add reference to it?

[wutao, 2017/04/03 16:16:04]

Created a http://crbug.com/707800 and added it to the main bug.

+extern const char kAshEnableSmoothScreenRotationAnimationName[];
+
+// Description for the flag to enable smooth rotation animations.
+extern const char kAshEnableSmoothScreenRotationAnimationDescription[];
+
 // Description for the flag that sets material design ink drop animation speed
 // of fast.
 extern const char kMaterialDesignInkDropAnimationFast[];
 
 // Description for the flag that sets material design ink drop anation speeds of
 // slow.
 extern const char kMaterialDesignInkDropAnimationSlow[];
 
 // Name for the flag that sets the material design ink drop animation speed.
 extern const char kMaterialDesignInkDropAnimationSpeedName[];
@@ skipping 2347 matching lines @@
 
 // Description of the about: flag enabling emoji, handwriting and voice input on
 // opt-in IME menu.
 extern const char kEnableEhvInputDescription[];
 
 #endif  // #if defined(OS_CHROMEOS)
 
 }  // namespace flag_descriptions
 
 #endif  // CHROME_BROWSER_FLAG_DESCRIPTIONS_H_