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

ui/gl/gl_surface.cc

Index: ui/gl/gl_surface.cc
diff --git a/ui/gl/gl_surface.cc b/ui/gl/gl_surface.cc
index f09aa35924daf21f1ab19a5eb57ba463eb8e011c..9552071e793ac43f0cbcfa872987ecf5e45d3581 100644
--- a/ui/gl/gl_surface.cc
+++ b/ui/gl/gl_surface.cc
@@ -69,6 +69,9 @@ bool GLSurface::InitializeOneOff() {
     if (CommandLine::ForCurrentProcess()->HasSwitch(
         switches::kEnableGPUServiceLogging))
       InitializeDebugGLBindings();
+    if (CommandLine::ForCurrentProcess()->HasSwitch(
+            switches::kDisableGLDrawingForTests))
+      InitializeStubGLBindings();

[no sievers, 2013/12/20 23:27:58]

The only caveat with that is that it would potentially not work with a function
specified as a stub in the generator script which is part of an extension. In
that case we would lazily call InitializeExtensionBindings() from the first
MakeCurrent(), which will override them again.

[danakj, 2013/12/20 23:29:38]

Ya, I noticed for the debug bindings, the generate_bindings script sets up a
bool and when it sets up extension bindings, it will check that bool and set up
debug bindings implicitly for the extensions at that time.

Since we don't need that now, we can ignore it, and use the same mechanism if we
wanted it, I think?

   }
   return initialized;
 }