Make RTCStatsReport::ToString() return JSON-parseable string.

webrtc/stats/BUILD.gn

 # Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../webrtc.gni")
 
@@ skipping 43 matching lines @@
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
 
     deps = [
       ":rtc_stats",
       ":rtc_stats_test_utils",
       "../api:rtc_stats_api",
       "../rtc_base:rtc_base_approved",
       "../rtc_base:rtc_base_tests_main",
       "../rtc_base:rtc_base_tests_utils",
+      "../rtc_base:rtc_json",
       "../system_wrappers:metrics_default",
       "//testing/gmock",
     ]
 
     if (is_android) {
       deps += [ "//testing/android/native_test:native_test_native_code" ]
     }
   }
 }