Widevine Metrics System

This change is the complete Widevine metrics system. It will
measure and record runtime information about what is happening
in the CDM - such as errors and throughput.

Bug: 33745339
Bug: 26027857
Change-Id: Ic9a82074f1e2b72c72d751b235f8ae361232787d

libwvdrmengine/cdm/core/include/cdm_engine.h

@@ -13,6 +13,7 @@
 #include "lock.h"
 #include "oemcrypto_adapter.h"
 #include "scoped_ptr.h"
+#include "timer_metric.h"
 #include "wv_cdm_constants.h"
 #include "wv_cdm_types.h"
 
@@ -210,6 +211,8 @@ class CdmEngine {
   // dead lock.
   virtual void OnTimerEvent();
 
+  virtual metrics::MetricsGroup* GetMetrics() { return &metrics_; }
+
  private:
   // private methods
   CdmResponseType OpenSession(const CdmKeySystem& key_system,
@@ -231,6 +234,18 @@ class CdmEngine {
   void CloseExpiredReleaseSessions();
 
   // instance variables
+
+
+  /*
+   * The metrics group must be the first variable declared to ensure
+   * that it is the last member destroyed so that no child members
+   * try to use a reference to it after it is destroyed. This will
+   * ensure that all data has been properly recorded in the group before
+   * it is published.
+   */
+  metrics::MetricsGroup metrics_;
+  metrics::TimerMetric life_span_;
+
   CdmSessionMap sessions_;
   CdmReleaseKeySetMap release_key_sets_;
   scoped_ptr<CertificateProvisioning> cert_provisioning_;