[Ozone] Explicitly whilelist valid GL platforms and fail GL initialization otherwise

NOTRY=true

Review URL: https://codereview.chromium.org/216433008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@260330 0039d316-1c4b-4281-b951-d872f2087c98

ui/gl/gl_surface_ozone.cc

@@ -29,10 +29,14 @@ bool GLSurface::InitializeOneOffInternal() {
         LOG(ERROR) << "GLSurfaceEGL::InitializeOneOff failed.";
         return false;
       }
+
+      return true;
+    case kGLImplementationOSMesaGL:
+    case kGLImplementationMockGL:
+      return true;
     default:
-      break;
+      return false;
   }
-  return true;
 }
 
 // static