[Chromecast] Add method to CastCdm for the session expiration updating.

Allows derived classes to access/run the SessionExpirationUpdateCB that
gets passed in to Initialize(). This follows the same pattern as the
other session callbacks in CastCdm (OnSessionClosed(),
OnSessionKeysChange()).

BUG=

Review-Url: https://codereview.chromium.org/2847923002
Cr-Commit-Position: refs/heads/master@{#467825}

chromecast/media/cdm/cast_cdm.cc

@@ -132,6 +132,11 @@ void CastCdm::OnSessionKeysChange(const std::string& session_id,
     player_tracker_impl_->NotifyNewKey();
 }
 
+void CastCdm::OnSessionExpirationUpdate(const std::string& session_id,
+                                        base::Time new_expiry_time) {
+  session_expiration_update_cb_.Run(session_id, new_expiry_time);
+}
+
 void CastCdm::KeyIdAndKeyPairsToInfo(const ::media::KeyIdAndKeyPairs& keys,
                                      ::media::CdmKeysInfo* keys_info) {
   DCHECK(keys_info);

chromecast/media/cdm/cast_cdm.h

@@ -16,6 +16,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/sequenced_task_runner_helpers.h"
 #include "base/threading/thread_checker.h"
+#include "base/time/time.h"
 #include "chromecast/media/base/media_resource_tracker.h"
 #include "chromecast/media/cdm/cast_cdm_context.h"
 #include "chromecast/public/media/cast_key_status.h"
@@ -82,6 +83,8 @@ class CastCdm : public ::media::ContentDecryptionModule {
   void OnSessionKeysChange(const std::string& session_id,
                            bool newly_usable_keys,
                            ::media::CdmKeysInfo keys_info);
+  void OnSessionExpirationUpdate(const std::string& session_id,
+                                 base::Time new_expiry_time);
 
   void KeyIdAndKeyPairsToInfo(const ::media::KeyIdAndKeyPairs& keys,
                               ::media::CdmKeysInfo* key_info);