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

ash/common/ash_switches.cc

 // 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.
 
 #include "ash/common/ash_switches.h"
 
 #include "base/command_line.h"
 #include "base/sys_info.h"
 
 namespace ash {
@@ skipping 43 matching lines @@
 // Enables the palette on every display, instead of only the internal one.
 const char kAshEnablePaletteOnAllDisplays[] =
     "ash-enable-palette-on-all-displays";
 
 // Enables the observation of accelerometer events to enter touch-view mode.
 const char kAshEnableTouchView[] = "enable-touchview";
 
 // Enables mirrored screen.
 const char kAshEnableMirroredScreen[] = "ash-enable-mirrored-screen";
 
+// Enables a smoother animation for screen rotation.
+const char kAshEnableSmoothScreenRotationAnimation[] =
+    "ash-enable-smooth-screen-rotation-animation";

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

you may omit "Animation/-animation" as it's obvious. up to you.

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

Removed as suggested.

+
 // Specifies the estimated time (in milliseconds) from VSYNC event until when
 // visible light can be noticed by the user.
 const char kAshEstimatedPresentationDelay[] =
     "ash-estimated-presentation-delay";
 
 // Enables the palette next to the status area.
 const char kAshForceEnablePalette[] = "ash-force-enable-palette";
 
 // Enables required things for the selected UI mode, regardless of whether the
 // Chromebook is currently in the selected UI mode.
@@ skipping 31 matching lines @@
 bool ConstrainPointerToRoot() {
   const char kAshConstrainPointerToRoot[] = "ash-constrain-pointer-to-root";
 
   return base::SysInfo::IsRunningOnChromeOS() ||
          base::CommandLine::ForCurrentProcess()->HasSwitch(
              kAshConstrainPointerToRoot);
 }
 
 }  // namespace switches
 }  // namespace ash