Mark HTMLMediaElement media tracks functionality as stable

third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in

Index: third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
diff --git a/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in b/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
index f902f6b84bebab98b7e8a126efbccba319707b06..de2292cb1037d675a5bc55375356fce2da8ece91 100644
--- a/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
+++ b/third_party/WebKit/Source/platform/RuntimeEnabledFeatures.in
@@ -30,7 +30,6 @@
 Accelerated2dCanvas status=stable, settable_from_internals=True
 AlwaysUseComplexText status=stable
 AudioOutputDevices status=stable
-AudioVideoTracks status=experimental

[mlamouri (slow - plz ping), 2016/08/17 09:09:39]

Usually, we mark the status as "stable" for a release or two before removing the
flag entirely. Is there a reason I'm missing why you prefer to drop the flag?

[servolk, 2016/08/17 15:56:22]

No reason, I just have no prior experience with moving features to stable and
based on the comment at line 17 above, which says '... stable features should be
rare ...' I've thought it would be better to remove the flag entirely, since
there are few places that need to be updated (I believe I got every single place
that need to be updated in this CL) and so it would be easy to remove. I can
mark the feature as 'stable' for now if that's the preferred way.

[wolenetz, 2016/08/18 00:10:50]

+1 to marking stable rather than ripping all the gates out.
Note that I'm investigating an MSE audio/videoTrack-related w3c test suite
failure at the moment (it looks like we need to fire 'change' at
{audio,video}Tracks when selected/enabled track changes. Or maybe the new test
suite test is doing something wrong. I'll fix one or both of Chromium and w3c
test suite shortly. Late changes like what I'll probably need to do further
justify marking 'stable' instead of ripping out the gates.

 Auxclick status=experimental
 BackgroundSync status=stable
 BackspaceDefaultHandler status=test