Add PlayerTracker and BrowserCdm interfaces.

media/cdm/player_tracker_impl.h

Index: media/cdm/player_tracker_impl.h
diff --git a/media/cdm/player_tracker_impl.h b/media/cdm/player_tracker_impl.h
new file mode 100644
index 0000000000000000000000000000000000000000..bcbeaf8c3c2ac6b5a76a5c1ff4824b08a8b42b43
--- /dev/null
+++ b/media/cdm/player_tracker_impl.h
@@ -0,0 +1,54 @@
+// Copyright 2014 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 MEDIA_CDM_PLAYER_TRACKER_IMPL_H_
+#define MEDIA_CDM_PLAYER_TRACKER_IMPL_H_
+
+#include <map>
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/threading/thread_checker.h"
+#include "media/base/media_export.h"
+#include "media/base/player_tracker.h"
+
+namespace media {
+
+// A common implementation that can be shared by different PlayerTracker
+// implementations. This class is not thread safe and should only be called
+// on one thread.
+class MEDIA_EXPORT PlayerTrackerImpl : public PlayerTracker {
+ public:
+  PlayerTrackerImpl();
+  virtual ~PlayerTrackerImpl();
+
+  // PlayerTracker implementation.
+  virtual int RegisterPlayer(const base::Closure& new_key_cb,
+                             const base::Closure& cdm_unset_cb) OVERRIDE;
+  virtual void UnregisterPlayer(int registration_id) OVERRIDE;
+
+  // Helpers methods to fire registered callbacks.
+  void NotifyNewKey();
+  void NotifyCdmUnset();
+
+ private:
+  struct PlayerCallbacks {
+    PlayerCallbacks(base::Closure new_key_cb, base::Closure cdm_unset_cb);
+    ~PlayerCallbacks();
+
+    base::Closure new_key_cb;
+    base::Closure cdm_unset_cb;
+  };
+
+  int next_registration_id_;
+  std::map<int, PlayerCallbacks> player_callbacks_map_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(PlayerTrackerImpl);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_CDM_PLAYER_TRACKER_IMPL_H_