Add about://flags flag to disable GPU canvas

BUG=none
TEST=Tested locally that the flag works as intended
Review URL: https://chromiumcodereview.appspot.com/10535036

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@140820 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index d6d8c5e..c44734d 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -197,6 +197,13 @@
     MULTI_VALUE_TYPE(kThreadedCompositingModeChoices)
   },
   {
+    "disable-accelerated-2d-canvas",
+    IDS_FLAGS_DISABLE_ACCELERATED_2D_CANVAS_NAME,
+    IDS_FLAGS_DISABLE_ACCELERATED_2D_CANVAS_DESCRIPTION,
+    kOsAll,
+    SINGLE_VALUE_TYPE(switches::kDisableAccelerated2dCanvas)
+  },
+  {
     "disable-deferred-2d-canvas",
     IDS_FLAGS_DISABLE_DEFERRED_2D_CANVAS_NAME,
     IDS_FLAGS_DISABLE_DEFERRED_2D_CANVAS_DESCRIPTION,