Changed name of MediaStreamImpl to UserMediaClientImpl.

UserMediaClientImpl's purpose is to implement blink::WebUserMediaClient and does not implement a MediaStream. Thus the class is renamed to reflect this.

BUG=409560

Review URL: https://codereview.chromium.org/524363003

Cr-Commit-Position: refs/heads/master@{#293132}

content/content_renderer.gypi

@@ -607,8 +607,7 @@
       'renderer/media/media_stream_audio_sink_owner.h',
       'renderer/media/media_stream_audio_track_sink.h',
       'renderer/media/media_stream_center.cc',
-      'renderer/media/media_stream_dispatcher.cc',
-      'renderer/media/media_stream_impl.cc',
+      'renderer/media/media_stream_dispatcher.cc',      
       'renderer/media/media_stream_registry_interface.h',
       'renderer/media/media_stream_audio_source.cc',
       'renderer/media/media_stream_audio_source.h',
@@ -650,6 +649,7 @@
       'renderer/media/rtc_video_encoder_factory.h',
       'renderer/media/rtc_video_renderer.cc',
       'renderer/media/rtc_video_renderer.h',
+      'renderer/media/user_media_client_impl.cc',
       'renderer/media/video_source_handler.cc',
       'renderer/media/video_source_handler.h',
       'renderer/media/video_track_adapter.cc',

content/content_tests.gypi

@@ -794,7 +794,6 @@
             'renderer/media/media_stream_audio_processor_unittest.cc',
             'renderer/media/media_stream_constraints_util_unittest.cc',
             'renderer/media/media_stream_dispatcher_unittest.cc',
-            'renderer/media/media_stream_impl_unittest.cc',
             'renderer/media/media_stream_video_capture_source_unittest.cc',
             'renderer/media/media_stream_video_source_unittest.cc',
             'renderer/media/media_stream_video_track_unittest.cc',
@@ -807,6 +806,7 @@
             'renderer/media/mock_media_constraint_factory.cc',
             'renderer/media/rtc_peer_connection_handler_unittest.cc',
             'renderer/media/rtc_video_decoder_unittest.cc',
+            'renderer/media/user_media_client_impl_unittest.cc',
             'renderer/media/video_source_handler_unittest.cc',
             'renderer/media/webrtc/media_stream_remote_video_source_unittest.cc',
             'renderer/media/webrtc/media_stream_track_metrics_unittest.cc',

content/renderer/media/media_stream_audio_source.cc

@@ -53,10 +53,10 @@ void MediaStreamAudioSource::AddTrack(
                                                     constraints,
                                                     this)) {
       // The source failed to start.
-      // MediaStreamImpl rely on the |stop_callback| to be triggered when the
-      // last track is removed from the source. But in this case, the source is
-      // is not even started. So we need to fail both adding the track and
-      // trigger |stop_callback|.
+      // UserMediaClientImpl rely on the |stop_callback| to be triggered when
+      // the last track is removed from the source. But in this case, the
+      // source is is not even started. So we need to fail both adding the
+      // track and trigger |stop_callback|.
       callback.Run(this, MEDIA_DEVICE_TRACK_START_FAILURE, "");
       StopSource();
       return;

content/renderer/media/media_stream_dispatcher.cc

@@ -208,7 +208,7 @@ void MediaStreamDispatcher::CloseDevice(const std::string& label) {
 }
 
 void MediaStreamDispatcher::OnDestruct() {
-  // Do not self-destruct.  MediaStreamImpl owns |this|.
+  // Do not self-destruct. UserMediaClientImpl owns |this|.
 }
 
 bool MediaStreamDispatcher::Send(IPC::Message* message) {