Support offscreen contexts which own their backing surface

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 70d6e1850a216d0abfa940b74d7f63467b328eac..69a2fbb0c80274025faad23cb4ddfbdfe27d5e7f 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -5510,6 +5510,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_FLAGS_WEBVR_DESCRIPTION" desc="Description for the flag to enable WebVR APIs.">
         Enabling this option allows web applications to access experimental Virtual Reality APIs.
       </message>
+      <message name="IDS_FLAGS_WEBVR_EXPERIMENTAL_RENDERING_NAME" desc="Name of the 'Enable WebVR experimental optimizations' flag.">
+        WebVR experimental rendering optimizations
+      </message>
+      <message name="IDS_FLAGS_WEBVR_EXPERIMENTAL_RENDERING_DESCRIPTION" desc="Description for the flag to enable experimental WebVR rendering optimizations.">
+        Enabling this option activates experimental rendering path optimizations for WebVR.
+      </message>
       <message name="IDS_FLAGS_GAMEPAD_EXTENSIONS_NAME" desc="Name of the flag which allows users to enable experimental extensions to the Gamepad API.">
         Gamepad Extensions
       </message>