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

chrome/browser/ui/webui/gpu_internals_ui.cc

Index: chrome/browser/ui/webui/gpu_internals_ui.cc
diff --git a/chrome/browser/ui/webui/gpu_internals_ui.cc b/chrome/browser/ui/webui/gpu_internals_ui.cc
index 4d79705e01a53f6b98c9cb47e76c0bf5122b756c..4eae479862c8c0d3b543cd7589e8cb1dab306560 100644
--- a/chrome/browser/ui/webui/gpu_internals_ui.cc
+++ b/chrome/browser/ui/webui/gpu_internals_ui.cc
@@ -6,6 +6,7 @@
 
 #include <string>
 
+#include "ash/ash_switches.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
@@ -283,6 +284,14 @@ Value* GetFeatureStatus() {
           "Accelerated video decode has been disabled, either via about:flags"
           " or command line.",
           true
+      },
+      {
+          "panel_fitting",
+          flags & content::GPU_FEATURE_TYPE_PANEL_FITTING,
+          command_line.HasSwitch(ash::switches::kAshDisablePanelFitting),
+          "Panel fitting is unavailable, either disabled at the command"
+          " line or not supported by the current system.",
+          false
       }
   };
   const size_t kNumFeatures = sizeof(kGpuFeatureInfo) / sizeof(GpuFeatureInfo);