Abstract OSMesa from the Layout tests

ui/gl/gl_implementation.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_implementation.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <string>
@@ skipping 62 matching lines @@
 
 GLImplementation GetNamedGLImplementation(const std::string& name) {
   for (size_t i = 0; i < arraysize(kGLImplementationNamePairs); ++i) {
     if (name == kGLImplementationNamePairs[i].name)
       return kGLImplementationNamePairs[i].implementation;
   }
 
   return kGLImplementationNone;
 }
 
+GLImplementation GetSoftwareGLImplementation() {
+  return kGLImplementationOSMesaGL;
+}
+
 const char* GetGLImplementationName(GLImplementation implementation) {
   for (size_t i = 0; i < arraysize(kGLImplementationNamePairs); ++i) {
     if (implementation == kGLImplementationNamePairs[i].implementation)
       return kGLImplementationNamePairs[i].name;
   }
 
   return "unknown";
 }
 
 void SetGLImplementation(GLImplementation implementation) {
@@ skipping 146 matching lines @@
   base::NativeLibrary library = base::LoadNativeLibrary(filename, &error);
   if (!library) {
     LOG(ERROR) << "Failed to load " << filename.MaybeAsASCII() << ": "
                << error.ToString();
     return NULL;
   }
   return library;
 }
 
 }  // namespace gl