Disable accelerated 2d canvas by default. Add an --enable-accelerated-2d-canvas flag

chrome/app/generated_resources.grd

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 <grit base_dir="." latest_public_release="0" current_release="1"
@@ skipping 4623 matching lines @@
       <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_ACCELERATED_CANVAS_2D_NAME" desc="Name of the 'GPU Accelerated Canvas 2D' lab.">
+        GPU Accelerated Canvas 2D
+      </message>
+      <message name="IDS_FLAGS_ACCELERATED_CANVAS_2D_DESCRIPTION" desc="Description of the 'GPU Accelerated Canvas 2D' lab.">
+        Enables higher performance of canvas tags with a 2D context by rendering using Graphics Processor Unit (GPU) hardware.
+      </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.">
         Enables canvas elements to use 3D graphics via the WebGL API.
       </message>
       <message name="IDS_FLAGS_PRINT_PREVIEW_NAME" desc="Name of the 'Print Preview' lab.">
         Print Preview
       </message>
       <message name="IDS_FLAGS_PRINT_PREVIEW_DESCRIPTION" desc="Description of the 'Print Preview' lab.">
@@ skipping 9936 matching lines @@
     </messages>
     <structures fallback_to_english="true">
       <!-- Make sure these stay in sync with the structures in generated_resources.grd. -->
       <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>