Add histogram WebRTC.UserMediaRequest.NoResultState to track user media requests with no result.

content/renderer/media/webrtc_uma_histograms.h

 // Copyright (c) 2012 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 CONTENT_RENDERER_MEDIA_WEBRTC_UMA_HISTOGRAMS_H_
 #define CONTENT_RENDERER_MEDIA_WEBRTC_UMA_HISTOGRAMS_H_
 
 #include "base/memory/singleton.h"
 #include "base/threading/non_thread_safe.h"
 #include "content/common/content_export.h"
 #include "content/public/common/media_stream_request.h"
 
 namespace content {
 
+// Used to investigate where UserMediaRequests end up.
+// Only UserMediaRequests that do not log with LogUserMediaRequestResult
+// should call LogUserMediaRequestWithNoResult.
+//
+// Elements in this enum should not be deleted or rearranged; the only
+// permitted operation is to add new elements before
+// NUM_MEDIA_STREAM_REQUEST_WITH_NO_RESULT.
+enum MediaStreamRequestState {
+  MEDIA_STREAM_REQUEST_EXPLICITLY_CANCELLED = 0,
+  MEDIA_STREAM_REQUEST_NOT_GENERATED = 1,
+  MEDIA_STREAM_REQUEST_PENDING_MEDIA_TRACKS = 2,
+  NUM_MEDIA_STREAM_REQUEST_WITH_NO_RESULT
+};
+
+void LogUserMediaRequestWithNoResult(MediaStreamRequestState state);
 void LogUserMediaRequestResult(MediaStreamRequestResult result);
 
 // Helper enum used for histogramming calls to WebRTC APIs from JavaScript.
 enum JavaScriptAPIName {
   WEBKIT_GET_USER_MEDIA,
   WEBKIT_PEER_CONNECTION,
   WEBKIT_DEPRECATED_PEER_CONNECTION,
   WEBKIT_RTC_PEER_CONNECTION,
   WEBKIT_GET_MEDIA_DEVICES,
   INVALID_NAME
@@ skipping 52 matching lines @@
 
   int num_streams_;
   bool has_used_api_[INVALID_NAME];
 
   DISALLOW_COPY_AND_ASSIGN(PerSessionWebRTCAPIMetrics);
 };
 
 } //  namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_WEBRTC_UMA_HISTOGRAMS_H_