Detect AudioInputStream muting and propagate to MediaStreamAudioSource.

third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.cpp

Index: third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.cpp
diff --git a/third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.cpp b/third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.cpp
index 10c2e52354652c43602fb7dd5f62b5aeb090598b..10fb1add97279ffc66ea7e544b61d9c079eced15 100644
--- a/third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.cpp
+++ b/third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.cpp
@@ -72,6 +72,11 @@ MediaStreamTrack::MediaStreamTrack(ExecutionContext* context,
       constraints_() {
   component_->Source()->AddObserver(this);
 
+  // If the source is already non-live at this point, the observer won't have
+  // been called. Check the state manually.
+  if (ready_state_ != component_->Source()->GetReadyState())
+    SourceChangedState();

[Guido Urdaneta, 2017/06/02 13:45:34]

Perhaps you should postpone the blink work to a follow-up CL because it requires
a little more work than this.
The spec says the only valid ready states are live and ended, but this change
will introduce a "muted" ready state which does not exist in the spec.
Can you introduce a test (possibly browser test, but maybe layout test) to check
that muting changes the muted attribute, but keeps the readyState as "live"?

[ossu-chromium, 2017/06/02 13:53:19]

Sounds good. I believe this should work as intended, since I've copied the blink
integration from the video side, but it really should be tested properly. The
rest of the code can land without this change, as well. It just won't pick up
the initial change.

[ossu-chromium, 2017/06/02 14:07:21]

Just checked: readyState goes to "muted" with this CL. Though the spec only has
"live" and "ended", MediaStreamSource in blink has three states (and did before
my change), so it's quite possible I've misunderstood how they're supposed to
interact. It's also possible blink should report "live" even though the source
goes to muted. I'll keep the part setting the ReadyState out of this CL as well
for now, so this CL only covers the propagation up into MediaStreamAudioSource.

[Guido Urdaneta, 2017/06/02 14:16:40]

MediaStreamSource was probably designed for an older version of the spec that
included "muted" as a readyState.
It can be made spec-compliant without many changes, but it's probably better to
do that in a follow-up CL.

+
   if (component_->Source() &&
       component_->Source()->GetType() == MediaStreamSource::kTypeVideo) {
     // ImageCapture::create() only throws if |this| track is not of video type.