Change from custom Lock to std::mutex.

[ Merge of http://go/wvgerrit/67884 ]

Now that we can use C++11, we should use the cross-platform std::mutex
type, not the custom pthread version.

Bug: 111850982
Test: WV unit/integration tests
Change-Id: If2fde2836826c5184609e6b1f3a6511206bd4594

libwvdrmengine/cdm/include/wv_content_decryption_module.h

@@ -7,13 +7,13 @@
 
 #include <map>
 #include <memory>
+#include <mutex>
 
 #include <utils/RefBase.h>
 
 #include "cdm_identifier.h"
 #include "disallow_copy_and_assign.h"
 #include "file_store.h"
-#include "lock.h"
 #include "metrics.pb.h"
 #include "timer.h"
 #include "wv_cdm_types.h"
@@ -165,14 +165,14 @@ class WvContentDecryptionModule : public android::RefBase, public TimerHandler {
   void DisablePolicyTimer();
   void OnTimerEvent();
 
-  static Lock session_sharing_id_generation_lock_;
-  Lock policy_timer_lock_;
+  static std::mutex session_sharing_id_generation_lock_;
+  std::mutex policy_timer_lock_;
   Timer policy_timer_;
 
   // instance variables
   // This manages the lifetime of the CDM instances.
   std::map<CdmIdentifier, CdmInfo> cdms_;
-  Lock cdms_lock_;
+  std::mutex cdms_lock_;
 
   // This contains weak pointers to the CDM instances contained in |cdms_|.
   std::map<std::string, CdmEngine*> cdm_by_session_id_;