Add about:flags entry to disable WebGL.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 4df2c0661edcb7bce7227b30fa6d90042a5cc8ff..56c23431fe987565f92d9f2cbbb44209c23cfc41 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -20,6 +20,7 @@
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "content/browser/user_metrics.h"
+#include "content/common/content_switches.h"
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/gfx/gl/gl_switches.h"
@@ -167,6 +168,13 @@ const Experiment kExperiments[] = {
     kOsAll,
     SINGLE_VALUE_TYPE(switches::kDisableGpuVsync)
   },
+  {
+    "disable-webgl",
+    IDS_FLAGS_DISABLE_WEBGL_NAME,
+    IDS_FLAGS_DISABLE_WEBGL_DESCRIPTION,
+    kOsAll,
+    SINGLE_VALUE_TYPE(switches::kDisableExperimentalWebGL)
+  },
   // Exposed on all platforms until there is a workaround for easy access to
   // the native print dialog for users that need it. Once that's done, revert
   // back to: