Implement MediaStreamTrack contentHint skeleton.

third_party/WebKit/public/platform/WebMediaStreamTrack.h

Index: third_party/WebKit/public/platform/WebMediaStreamTrack.h
diff --git a/third_party/WebKit/public/platform/WebMediaStreamTrack.h b/third_party/WebKit/public/platform/WebMediaStreamTrack.h
index d67453bccaae29ddf91810880cb27bf326edc837..d9191b721badcf0e80afb731e5014a181312a689 100644
--- a/third_party/WebKit/public/platform/WebMediaStreamTrack.h
+++ b/third_party/WebKit/public/platform/WebMediaStreamTrack.h
@@ -60,6 +60,14 @@ class WebMediaStreamTrack {
     virtual void getSettings(Settings&) = 0;
   };
 
+  enum class ContentHintType {
+    None,
+    AudioSpeech,
+    AudioMusic,
+    VideoFluid,
+    VideoDetailed
+  };
+
   WebMediaStreamTrack() {}
   WebMediaStreamTrack(const WebMediaStreamTrack& other) { assign(other); }
   ~WebMediaStreamTrack() { reset(); }
@@ -82,6 +90,7 @@ class WebMediaStreamTrack {
   BLINK_PLATFORM_EXPORT WebMediaStreamSource source() const;
   BLINK_PLATFORM_EXPORT bool isEnabled() const;
   BLINK_PLATFORM_EXPORT bool isMuted() const;
+  BLINK_PLATFORM_EXPORT ContentHintType contentHint() const;
 
   // Extra data associated with this WebMediaStream.
   // If non-null, the extra data pointer will be deleted when the object is