Use stub GL draw/clear calls for browser tests that do not need pixels.

ui/gl/gl_gl_api_implementation.cc

Index: ui/gl/gl_gl_api_implementation.cc
diff --git a/ui/gl/gl_gl_api_implementation.cc b/ui/gl/gl_gl_api_implementation.cc
index eade3cedaf5e6df54041372b964335aa7937edca..ecf8a04a3c1bb19eb45da7c649c7b9f77c78fd4f 100644
--- a/ui/gl/gl_gl_api_implementation.cc
+++ b/ui/gl/gl_gl_api_implementation.cc
@@ -203,6 +203,8 @@ void InitializeDebugGLBindingsGL() {
   g_driver_gl.InitializeDebugBindings();
 }
 
+void InitializeStubGLBindingsGL() { g_driver_gl.InitializeStubBindings(); }
+
 void ClearGLBindingsGL() {
   if (g_real_gl) {
     delete g_real_gl;