Add disable-gpu-vsync to about:flags

chrome/app/generated_resources.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!--
 This file contains definitions of resources that will be translated for each
 locale. OS values are passed through from Python's sys.platform:
 
   win32 - Windows
   darwin - Mac
   linux2 - Linux (both Views and GTK+)
 
@@ skipping 4131 matching lines @@
       </message>
       <message name="IDS_FLAGS_FORCE_COMPOSITING_MODE_DESCRIPTION" desc="Description of the 'Force compositing mode' lab.">
         Uses GPU accelerated compositing on all pages, not just those that include GPU-accelerated layers.
       </message>
       <message name="IDS_FLAGS_IGNORE_GPU_BLACKLIST_NAME" desc="Name of the 'Ignore GPU blacklist' lab.">
         Override software rendering list
       </message>
       <message name="IDS_FLAGS_IGNORE_GPU_BLACKLIST_DESCRIPTION" desc="Description of the 'Ignore GPU blacklist' lab.">
         Overrides the built-in software rendering list and enables GPU-acceleration on unsupported system configurations.
       </message>
+      <message name="IDS_FLAGS_DISABLE_GPU_VSYNC_NAME" desc="Name of the 'Disable GPU VSync' lab.">
+        Disable GPU VSync
+      </message>
+      <message name="IDS_FLAGS_DISABLE_GPU_VSYNC_DESCRIPTION" desc="Description of the 'Disable GPU VSync' lab.">
+        Disables synchronization with the display's vertical refresh rate when GPU rendering. This allows frame rates to exceed
+        60 hertz. While useful for benchmarking purposes, this also results in visual tearing during rapid screen updates.
+      </message>
       <message name="IDS_FLAGS_WEBAUDIO_NAME" desc="Name of the 'Web Audio' lab.">
         Web Audio
       </message>
       <message name="IDS_FLAGS_WEBAUDIO_DESCRIPTION" desc="Description of the 'Web Audio' lab.">
         Enables the Web Audio API.
       </message>
       <message name="IDS_FLAGS_WEBGL_NAME" desc="Name of the 'WebGL' lab.">
         WebGL
       </message>
       <message name="IDS_FLAGS_WEBGL_DESCRIPTION" desc="Description of the 'WebGL' lab.">
@@ skipping 8334 matching lines @@
     </includes>
     <structures fallback_to_english="true">
       <structure name="IDD_CHROME_FRAME_FIND_DIALOG" file="cf_resources.rc" type="dialog" >
       </structure>
       <structure name="IDD_CHROME_FRAME_READY_PROMPT" file="cf_resources.rc" type="dialog" >
       </structure>
     </structures>
 
   </release>
 </grit>