Add PlayerTracker and BrowserCdm interfaces.

media/base/player_tracker.cc

Index: media/base/player_tracker.cc
diff --git a/media/audio/mock_audio_source_callback.cc b/media/base/player_tracker.cc
similarity index 56%
copy from media/audio/mock_audio_source_callback.cc
copy to media/base/player_tracker.cc
index da2be1cfa41c3cf8aa63b969fc9451dcc5dc3dbc..909aaecfe4586163b3e646237465dfa8a6c863c0 100644
--- a/media/audio/mock_audio_source_callback.cc
+++ b/media/base/player_tracker.cc
@@ -2,11 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "media/audio/mock_audio_source_callback.h"
+#include "media/base/player_tracker.h"
 
 namespace media {
 
-MockAudioSourceCallback::MockAudioSourceCallback() {}
-MockAudioSourceCallback::~MockAudioSourceCallback() {}
+PlayerTracker::PlayerTracker() {
+}
+
+PlayerTracker::~PlayerTracker() {
+}
 
 }  // namespace media