media: Add UMA and trace events for CDM creation.

media/blink/cdm_session_adapter.h

 // 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_BLINK_CDM_SESSION_ADAPTER_H_
 #define MEDIA_BLINK_CDM_SESSION_ADAPTER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 92 matching lines @@
 
   // Session ID to WebContentDecryptionModuleSessionImpl mapping.
   typedef base::hash_map<std::string,
                          base::WeakPtr<WebContentDecryptionModuleSessionImpl> >
       SessionMap;
 
   ~CdmSessionAdapter();
 
   // Callback for CreateCdm().
   void OnCdmCreated(const std::string& key_system,
+                    base::TimeTicks start_time,
                     blink::WebContentDecryptionModuleResult result,
                     scoped_ptr<MediaKeys> cdm,
                     const std::string& error_message);
 
   // Callbacks for firing session events.
   void OnSessionMessage(const std::string& session_id,
                         MediaKeys::MessageType message_type,
                         const std::vector<uint8_t>& message,
                         const GURL& legacy_destination_url);
   void OnSessionKeysChange(const std::string& session_id,
                            bool has_additional_usable_key,
                            CdmKeysInfo keys_info);
   void OnSessionExpirationUpdate(const std::string& session_id,
                                  const base::Time& new_expiry_time);
   void OnSessionClosed(const std::string& session_id);
   void OnLegacySessionError(const std::string& session_id,
                             MediaKeys::Exception exception_code,
                             uint32_t system_code,
                             const std::string& error_message);
 
   // Helper function of the callbacks.
   WebContentDecryptionModuleSessionImpl* GetSession(
       const std::string& session_id);
 
+  void ReportCdmCreationTimeUMA(base::TimeDelta cdm_creation_time);

[ddorwin, 2015/07/20 21:35:21]

static? At least const?

[ddorwin, 2015/07/20 21:35:21]

nit: "Time" makes it sound like, for example, the UTC time rather than duration.
See also the UMA naming comment.

Naming the variable "duration" would be at least an improvement even if the
function is harder to name.

Also, we probably don't need the "cdm_creation_" part as it's redundant.

[xhwang, 2015/07/20 22:11:57]

Can't be static since we need GetKeySystemUMAPrefix().
Done.

[xhwang, 2015/07/20 22:11:57]

See the reply about the UMA naming.
Done.

+
   scoped_ptr<MediaKeys> cdm_;
 
   SessionMap sessions_;
 
   std::string key_system_;
   std::string key_system_uma_prefix_;
 
+  // A unique ID to trace CdmSessionAdapter::CreateCdm() call and the matching
+  // OnCdmCreated() call.
+  uint32 trace_id_;
+
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<CdmSessionAdapter> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CdmSessionAdapter);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_CDM_SESSION_ADAPTER_H_