Fixes metrics collection during CdmEngine close.

This fixes a problem where a CdmEngine instance (and its sessions) could
be closed before its metrics could be collected. The change allows the
wv_content_decryption_module to extract metrics from instances about to
be closed. These are held until reported to the caller.

Test: Manually verified that collection is now occurring correctly. Also
added unit test: wv_cdm_metric_test.

This is a merge from wvgerrit/29069

Change-Id: If82bfd5cae3b72b9d14ab4741424a7ae7cc0a3a6

libwvdrmengine/cdm/include/wv_content_decryption_module.h

@@ -11,6 +11,7 @@
 #include "cdm_identifier.h"
 #include "file_store.h"
 #include "lock.h"
+#include "metrics.pb.h"
 #include "timer.h"
 #include "wv_cdm_types.h"
 
@@ -125,7 +126,8 @@ class WvContentDecryptionModule : public android::RefBase, public TimerHandler {
   // Validate a passed-in service certificate
   virtual bool IsValidServiceCertificate(const std::string& certificate);
 
-  // Retrieve the serialized metrics from the CDM.
+  // Retrieve the serialized metrics from CdmEngine and CdmSession instances
+  // that have been closed.
   virtual void GetSerializedMetrics(std::string* serialized_metrics);
 
  private:
@@ -142,6 +144,10 @@ class WvContentDecryptionModule : public android::RefBase, public TimerHandler {
   // Finds the CdmEngine instance for the given session id, returning NULL if
   // not found.
   CdmEngine* GetCdmForSessionId(const std::string& session_id);
+  // Closes CdmEngine instances that don't have any open sessions. Also stores
+  // metrics data for closed CdmEngine instances.
+  // Callers must acquire the cdms_lock_ before calling this method.
+  void CloseCdmsWithoutSessions();
 
   uint32_t GenerateSessionSharingId();
 
@@ -162,6 +168,9 @@ class WvContentDecryptionModule : public android::RefBase, public TimerHandler {
   // This contains weak pointers to the CDM instances contained in |cdms_|.
   std::map<std::string, CdmEngine*> cdm_by_session_id_;
 
+  // The metrics for cdm engines and sessions that have been closed.
+  drm_metrics::MetricsGroup metrics_;
+
   CORE_DISALLOW_COPY_AND_ASSIGN(WvContentDecryptionModule);
 };