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

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 2f503214cd0bdda466f8313b37a40b90d2b5c64b..60b964b505910ef7d6cbaa9f310453609c5795d6 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -3689,7 +3689,7 @@ From <ph name="DOWNLOAD_DOMAIN">$3<ex>example.com</ex></ph>
       </message>
 
       <message name="IDS_EXTENSION_PERMISSION_LINE" desc="Template for item in list of privileges that an extension or app has">
-          • <ph name="PERMISSION">$1<ex>Read and change all your data on the websites you visit</ex></ph>
+          • <ph name="PERMISSION">$1<ex>Read and change all your data on the websites you visit</ex></ph>
       </message>
       <message name="IDS_EXTENSION_RATING_COUNT" desc="Number of ratings an app or extensions has (displayed after star icons)">
         (<ph name="RATING_COUNT">$1<ex>46</ex></ph>)
@@ -5746,6 +5746,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
         <message name="IDS_FLAGS_ASH_ENABLE_MIRRORED_SCREEN_DESCRIPTION" desc="Description for the flag to enable the mirrored screen mode." translateable="false">
           Enable the mirrored screen mode. This mode flips the screen image horizontally.
         </message>
+        <message name="IDS_FLAGS_ASH_ENABLE_SMOOTH_SCREEN_ROTATION_ANIMATION_NAME" desc="Title for the flag to enable a smoother screen rotation animation." translateable="false">

[bruthig, 2017/03/30 18:28:24]

It appears vabr@ moved a lot of Ash command line flags to
chrome/browser/flag_descriptions.cc (See
https://codereview.chromium.org/2774203002).  Might want to double check with
them as to where these descriptions should be added.

[wutao, 2017/03/30 21:25:41]

You are right.

+          Enable a smoother screen rotation animation.

[bruthig, 2017/03/30 18:28:24]

nit: This is rather long for a name.  Consider the slightly shorter: 'Enable
smooth rotation animations'

[wutao, 2017/03/30 21:25:41]

Done.

+        </message>
+        <message name="IDS_FLAGS_ASH_ENABLE_SMOOTH_SCREEN_ROTATION_ANIMATION_DESCRIPTION" desc="Description for the flag to enable a smoother screen rotation animation." translateable="false">
+          Enable a smoother screen rotation animation.
+        </message>
         <message name="IDS_FLAGS_MATERIAL_DESIGN_INK_DROP_ANIMATION_FAST" desc="Description for the flag that sets material design ink drop animation speed of fast." translateable="false">
           Fast
         </message>