Creates a new license request latency metric

Previously, we did not have a license request latency metric. This is a
notable limitation in our metrics. This adds a metric that captures the
timing between a GenerateKeyRequest and an AddKey operation.

Bug: 72994956
Test: New unit tests. Google Play
Change-Id: If99c187399c02f9b5d4c355732af7588bbbefb11

libwvdrmengine/cdm/core/include/cdm_session.h

@@ -199,6 +199,12 @@ class CdmSession {
 
   bool UpdateUsageInfo();
 
+  CdmResponseType GenerateKeyRequestInternal(
+      const InitializationData& init_data, CdmLicenseType license_type,
+      const CdmAppParameterMap& app_parameters, CdmKeyRequest* key_request);
+  virtual CdmResponseType AddKeyInternal(const CdmKeyResponse& key_response);
+  void UpdateRequestLatencyTiming(CdmResponseType sts);
+
   // These setters are for testing only. Takes ownership of the pointers.
   void set_license_parser(CdmLicense* license_parser);
   void set_crypto_session(CryptoSession* crypto_session);
@@ -209,6 +215,8 @@ class CdmSession {
   metrics::SessionMetrics* metrics_;
   metrics::CryptoMetrics* crypto_metrics_;
   metrics::TimerMetric life_span_;
+  metrics::TimerMetric license_request_latency_;
+  CdmKeyRequestType key_request_type_;
 
   bool initialized_;
   bool closed_;  // Session closed, but final shared_ptr has not been released.