Add "panel_fitting" GPU feature type and use it for mirror mode.

content/browser/gpu/gpu_util.cc

Index: content/browser/gpu/gpu_util.cc
diff --git a/content/browser/gpu/gpu_util.cc b/content/browser/gpu/gpu_util.cc
index fdd8c729794db7bb94b34513893ee94de9dafd3b..f3862db01fc07e6ebb0abe7d86141bb0dabf0bd9 100644
--- a/content/browser/gpu/gpu_util.cc
+++ b/content/browser/gpu/gpu_util.cc
@@ -30,6 +30,7 @@ const char kGpuFeatureNameTextureSharing[] = "texture_sharing";
 const char kGpuFeatureNameAcceleratedVideoDecode[] = "accelerated_video_decode";
 const char kGpuFeatureName3dCss[] = "3d_css";
 const char kGpuFeatureNameAcceleratedVideo[] = "accelerated_video";
+const char kGpuFeatureNamePanelFitting[] = "panel_fitting";
 const char kGpuFeatureNameAll[] = "all";
 const char kGpuFeatureNameUnknown[] = "unknown";
 
@@ -109,6 +110,8 @@ GpuFeatureType StringToGpuFeatureType(const std::string& feature_string) {
     return content::GPU_FEATURE_TYPE_3D_CSS;
   if (feature_string == kGpuFeatureNameAcceleratedVideo)
     return content::GPU_FEATURE_TYPE_ACCELERATED_VIDEO;
+  if (feature_string == kGpuFeatureNamePanelFitting)
+    return content::GPU_FEATURE_TYPE_PANEL_FITTING;
   if (feature_string == kGpuFeatureNameAll)
     return content::GPU_FEATURE_TYPE_ALL;
   return content::GPU_FEATURE_TYPE_UNKNOWN;
@@ -139,6 +142,8 @@ std::string GpuFeatureTypeToString(GpuFeatureType type) {
       matches.push_back(kGpuFeatureName3dCss);
     if (type & content::GPU_FEATURE_TYPE_ACCELERATED_VIDEO)
       matches.push_back(kGpuFeatureNameAcceleratedVideo);
+    if (type & content::GPU_FEATURE_TYPE_PANEL_FITTING)
+      matches.push_back(kGpuFeatureNamePanelFitting);
     if (!matches.size())
       matches.push_back(kGpuFeatureNameUnknown);
   }