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_session.h

@@ -11,9 +11,11 @@
 #include "file_store.h"
 #include "initialization_data.h"
 #include "license.h"
+#include "metrics_group.h"
 #include "oemcrypto_adapter.h"
 #include "policy_engine.h"
 #include "scoped_ptr.h"
+#include "timer_metric.h"
 #include "wv_cdm_types.h"
 
 namespace wvcdm {
@@ -151,6 +153,8 @@ class CdmSession {
                                         CdmSigningAlgorithm algorithm,
                                         const std::string& signature);
 
+  virtual metrics::MetricsGroup* GetMetrics() { return &metrics_; }
+
  private:
   friend class CdmSessionTest;
 
@@ -166,6 +170,17 @@ class CdmSession {
   void set_file_handle(DeviceFiles* file_handle);
 
   // 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_;
+
   bool initialized_;
   CdmSessionId session_id_;
   scoped_ptr<CdmLicense> license_parser_;