Add Media.ArcGpuVideoDecodeAccelerator.InitializeResult to histograms

chrome/gpu/arc_video_accelerator.h

 // Copyright 2016 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 CHROME_GPU_ARC_VIDEO_ACCELERATOR_H_
 #define CHROME_GPU_ARC_VIDEO_ACCELERATOR_H_
 
 #include <vector>
 
 #include "base/files/scoped_file.h"
@@ skipping 38 matching lines @@
   uint32_t crop_top = 0;
   uint32_t crop_height = 0;
 };
 
 // The IPC interface between Android and Chromium for video decoding and
 // encoding. Input buffers are sent from Android side and get processed in
 // Chromium and the output buffers are returned back to Android side.
 class ArcVideoAccelerator {
  public:
   enum Result {
+    // Note: this enum is used for UMA reporting. The existing values should not
+    // be rearranged, reused or removed and any additions should include updates
+    // to UMA reporting and histograms.xml.
     SUCCESS = 0,
     ILLEGAL_STATE = 1,
     INVALID_ARGUMENT = 2,
     UNREADABLE_INPUT = 3,
     PLATFORM_FAILURE = 4,
     INSUFFICIENT_RESOURCES = 5,
+    RESULT_MAX = 6,
   };
 
   struct Config {
     enum DeviceType {
       DEVICE_ENCODER = 0,
       DEVICE_DECODER = 1,
     };
 
     DeviceType device_type = DEVICE_DECODER;
     size_t num_input_buffers = 0;
@@ skipping 82 matching lines @@
   // called.
   virtual void Flush() = 0;
 
   virtual ~ArcVideoAccelerator() {}
 };
 
 }  // namespace arc
 }  // namespace chromeos
 
 #endif  // CHROME_GPU_ARC_VIDEO_ACCELERATOR_H_