Add histogram WebRTC.UserMediaRequest.Events to allow to track getUserMedia failures and hangs.

content/renderer/media/webrtc_uma_histograms.cc

 // Copyright 2014 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.
 
 #include "content/renderer/media/webrtc_uma_histograms.h"
 
 #include "base/metrics/histogram.h"
 
 namespace content {
 
+void LogUserMediaRequestResult(MediaStreamRequestResult result) {
+  UMA_HISTOGRAM_ENUMERATION(
+      "WebRTC.UserMediaRequest.Result", result, NUM_MEDIA_REQUEST_RESULTS);
+}
+
 void UpdateWebRTCMethodCount(JavaScriptAPIName api_name) {
   DVLOG(3) << "Incrementing WebRTC.webkitApiCount for " << api_name;
   UMA_HISTOGRAM_ENUMERATION("WebRTC.webkitApiCount", api_name, INVALID_NAME);
   PerSessionWebRTCAPIMetrics::GetInstance()->LogUsageOnlyOnce(api_name);
 }
 
 PerSessionWebRTCAPIMetrics::~PerSessionWebRTCAPIMetrics() {
 }
 
 // static
@@ skipping 30 matching lines @@
     LogUsage(api_name);
   }
 }
 
 void PerSessionWebRTCAPIMetrics::ResetUsage() {
   for (size_t i = 0; i < arraysize(has_used_api_); ++i)
     has_used_api_[i] = false;
 }
 
 }  // namespace content