Let Contraints Controll Mute/Unmute Audio Local Playback For Desktop Sharing

content/renderer/media/user_media_client_impl.cc

Index: content/renderer/media/user_media_client_impl.cc
diff --git a/content/renderer/media/user_media_client_impl.cc b/content/renderer/media/user_media_client_impl.cc
index 10122a048a4468a368fd10747996b159811a8868..8d84135470838e60e13881acd6ab877cf72c85ec 100644
--- a/content/renderer/media/user_media_client_impl.cc
+++ b/content/renderer/media/user_media_client_impl.cc
@@ -85,6 +85,17 @@ void CopyBlinkRequestToStreamControls(const blink::WebUserMediaRequest& request,
         }
       }
     }
+
+    bool exact = request.audioConstraints().basic().disableLocalEcho.exact();

[Sergey Ulanov, 2016/10/12 22:21:01]

this doesn't look like a good variable name. Also it looks wrong to call exact()
if hasExcat() returns false. Why can't this code follow the same pattern that's
used above for hotword_enabled:
  if (request.audioConstraints().basic().disableLocalEcho.hasExact()) {
    controls->disable_local_echo =
         request.audioConstraints().basic().disableLocalEcho.exact();
  } else {
    controls->disable_local_echo =
        controls->audio.stream_source != kMediaStreamSourceDesktop;
  }

Or even this:
  controls->disable_local_echo =
     request.audioConstraints().basic().disableLocalEcho.hasExact()
        ? request.audioConstraints().basic().disableLocalEcho.exact()
        : controls->audio.stream_source != kMediaStreamSourceDesktop;

[qiangchen, 2016/10/12 22:49:54]

Done.

+    bool has_exact =
+        request.audioConstraints().basic().disableLocalEcho.hasExact();
+
+    if (has_exact) {
+      controls->disable_local_echo = exact;
+    } else {
+      controls->disable_local_echo =
+          controls->audio.stream_source != kMediaStreamSourceDesktop;
+    }
   }
   if (!request.videoConstraints().isNull()) {
     const blink::WebMediaTrackConstraintSet& video_basic =