Implement blacklist's force GPU capability in dual GPU machines.

content/browser/gpu/gpu_util.h

 // 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.
 
 #ifndef CONTENT_BROWSER_GPU_GPU_UTIL_H_
 #define CONTENT_BROWSER_GPU_GPU_UTIL_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
 #include "content/public/common/gpu_feature_type.h"
+#include "content/public/common/gpu_switching_option.h"
 
 class GpuBlacklist;
 
 namespace gpu_util {
 
 // Maps string to GpuFeatureType; returns GPU_FEATURE_TYPE_UNKNOWN if an
 // unknown name is input (case-sensitive).
 CONTENT_EXPORT content::GpuFeatureType StringToGpuFeatureType(
     const std::string& feature_string);
 
 // Gets a string version of a feature type for use in about:gpu. Will yield
 // strings from StringToGpuFeatureType, e.g.
 // GPU_FEATURE_TYPE_ACCELERATED_2D_CANVAS becomes "accelerated_2d_canvas"
 CONTENT_EXPORT std::string GpuFeatureTypeToString(
     content::GpuFeatureType feature);
 
 // Maps string to GpuSwitchingOption; returns GPU_SWITCHING_UNKNOWN if an
 // unknown name is input (case-sensitive).
 CONTENT_EXPORT content::GpuSwitchingOption StringToGpuSwitchingOption(
     const std::string& switching_string);
 
+// Gets a string version of a GpuSwitchingOption.
+CONTENT_EXPORT std::string GpuSwitchingOptionToString(
+    content::GpuSwitchingOption option);
+
 // Send UMA histograms about the enabled features.
 CONTENT_EXPORT void UpdateStats(
     const GpuBlacklist* blacklist, uint32 blacklisted_features);
 
 }  // namespace gpu_util
 
 #endif  // CONTENT_BROWSER_GPU_GPU_UTIL_H_