Add Promises for EME (Chromium side)

media/base/browser_cdm.h

Index: media/base/browser_cdm.h
diff --git a/media/base/browser_cdm.h b/media/base/browser_cdm.h
index 6e4e5cd39aa6f570726446bcf0a9631280e16e6f..b6b6044c4d7504af258e000f3115da9f38018d27 100644
--- a/media/base/browser_cdm.h
+++ b/media/base/browser_cdm.h
@@ -11,11 +11,29 @@
 namespace media {
 
 // Interface for browser side CDMs.
-class BrowserCdm : public MediaKeys, public PlayerTracker {
+class BrowserCdm : public PlayerTracker {
  public:
+  // TODO(jrummell): Update this to actually derive from MediaKeys
+  // (Use web_session_id rather than session_id).
+  typedef base::Callback<
+      void(uint32 session_id, const std::string& web_session_id)>
+      SessionCreatedCB;
+
+  typedef base::Callback<void(uint32 session_id,
+                              const std::vector<uint8>& message,
+                              const GURL& destination_url)> SessionMessageCB;
+
+  typedef base::Callback<void(uint32 session_id)> SessionReadyCB;
+
+  typedef base::Callback<void(uint32 session_id)> SessionClosedCB;
+
+  typedef base::Callback<void(uint32 session_id,
+                              media::MediaKeys::KeyError error_code,
+                              uint32 system_code)> SessionErrorCB;
+
   virtual ~BrowserCdm();
 
-  // MediaKeys implementation.
+  // MediaKeys-like implementation.
   virtual bool CreateSession(uint32 session_id,
                              const std::string& content_type,
                              const uint8* init_data,