media: Add UMA and trace events for CDM creation.

media/blink/cdm_session_adapter.h

Index: media/blink/cdm_session_adapter.h
diff --git a/media/blink/cdm_session_adapter.h b/media/blink/cdm_session_adapter.h
index d70e801ab9c69323d93d2bec1784488ddbf10033..192061410579c997250d49e59d4cf8919e2b7f4e 100644
--- a/media/blink/cdm_session_adapter.h
+++ b/media/blink/cdm_session_adapter.h
@@ -110,6 +110,7 @@ class CdmSessionAdapter : public base::RefCounted<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);
@@ -134,6 +135,8 @@ class CdmSessionAdapter : public base::RefCounted<CdmSessionAdapter> {
   WebContentDecryptionModuleSessionImpl* GetSession(
       const std::string& session_id);
 
+  void ReportTimeToCreateCdmUMA(base::TimeDelta cdm_creation_time) const;
+
   scoped_ptr<MediaKeys> cdm_;
 
   SessionMap sessions_;
@@ -141,6 +144,10 @@ class CdmSessionAdapter : public base::RefCounted<CdmSessionAdapter> {
   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_;