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

ui/gl/gl_surface.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gl/gl_surface.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 51 matching lines @@
                   InitializeOneOffInternal();
   }
 
   if (initialized) {
     DVLOG(1) << "Using "
              << GetGLImplementationName(GetGLImplementation())
              << " GL implementation.";
     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;
 }
 
 GLSurface::GLSurface() {}
 
 bool GLSurface::Initialize() {
   return true;
 }
 
@@ skipping 172 matching lines @@
   return surface_->GetFormat();
 }
 
 VSyncProvider* GLSurfaceAdapter::GetVSyncProvider() {
   return surface_->GetVSyncProvider();
 }
 
 GLSurfaceAdapter::~GLSurfaceAdapter() {}
 
 }  // namespace gfx