Move MediaStreamTrack contentHint to separate IDL.

BUG=chromium:653531
R=esprehn@chromium.org, mcasas@chromium.org

Review-Url: https://codereview.chromium.org/2578623002
Cr-Commit-Position: refs/heads/master@{#438603}

third_party/WebKit/Source/modules/mediastream/BUILD.gn

@@ -24,6 +24,7 @@ blink_modules_sources("mediastream") {
     "MediaStreamRegistry.h",
     "MediaStreamTrack.cpp",
     "MediaStreamTrack.h",
+    "MediaStreamTrackContentHint.h",
     "MediaStreamTrackEvent.cpp",
     "MediaStreamTrackEvent.h",
     "NavigatorMediaStream.cpp",

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

@@ -42,7 +42,6 @@ enum MediaStreamTrackState {
     readonly attribute DOMString label;
     attribute boolean enabled;
     readonly attribute boolean muted;
-    [RuntimeEnabled=MediaStreamTrackContentHint] attribute DOMString contentHint;
     attribute EventHandler onmute;
     attribute EventHandler onunmute;
     readonly attribute MediaStreamTrackState readyState;

third_party/WebKit/Source/modules/mediastream/MediaStreamTrackContentHint.h

+// Copyright 2016 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 MediaStreamTrackContentHint_h
+#define MediaStreamTrackContentHint_h
+
+#include "modules/mediastream/MediaStreamTrack.h"
+
+namespace blink {
+
+class MediaStreamTrackContentHint final {
+ public:
+  static String contentHint(const MediaStreamTrack& track) {
+    return track.contentHint();
+  }
+  static void setContentHint(MediaStreamTrack& track, const String& hint) {
+    track.setContentHint(hint);
+  }
+};
+
+}  // namespace blink
+
+#endif  // MediaStreamTrack_h

third_party/WebKit/Source/modules/mediastream/MediaStreamTrackContentHint.idl

+// Copyright 2016 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.
+
+// https://wicg.github.io/mst-content-hint/#extension-to-mediastreamtrack
+[
+  RuntimeEnabled=MediaStreamTrackContentHint,
+] partial interface MediaStreamTrack {
+    attribute DOMString contentHint;
+};

third_party/WebKit/Source/modules/modules_idl_files.gni

@@ -582,6 +582,7 @@ modules_dependency_idl_files =
           "mediasource/VideoTrackSourceBuffer.idl",
           "mediasource/HTMLVideoElementMediaSource.idl",
           "mediasource/URLMediaSource.idl",
+          "mediastream/MediaStreamTrackContentHint.idl",
           "mediastream/NavigatorMediaStream.idl",
           "mediastream/NavigatorUserMedia.idl",
           "mediastream/URLMediaStream.idl",