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/metrics/include/metrics_collections.h

@@ -140,7 +140,7 @@ class CryptoMetrics {
   EventMetric<OEMCryptoResult> oemcrypto_rewrap_device_rsa_key_;
   EventMetric<OEMCryptoResult> oemcrypto_rewrap_device_rsa_key_30_;
   EventMetric<CdmSecurityLevel, SecurityLevel> oemcrypto_security_level_;
-  EventMetric<uint8_t, SecurityLevel> oemcrypto_security_patch_level_;
+  EventMetric<uint16_t, SecurityLevel> oemcrypto_security_patch_level_;
   EventMetric<OEMCryptoResult> oemcrypto_select_key_;
   EventMetric<OEMCryptoResult, SecurityLevel> oemcrypto_supports_usage_table_;
   EventMetric<OEMCryptoResult> oemcrypto_update_usage_table_;

libwvdrmengine/cdm/metrics/src/metrics_collections.cpp

@@ -4,6 +4,7 @@
 
 #include <algorithm>
 
+#include "log.h"
 #include "metrics.pb.h"
 
 using drm_metrics::MetricsGroup;
@@ -438,6 +439,10 @@ EngineMetrics::EngineMetrics() :
 EngineMetrics::~EngineMetrics() {
   AutoLock kock(session_metrics_lock_);
   std::vector<SessionMetrics*>::iterator i;
+  if (!session_metrics_list_.empty()) {
+    LOGV("EngineMetrics::~EngineMetrics. Session count: %d",
+         session_metrics_list_.size());
+  }
   for (i = session_metrics_list_.begin(); i != session_metrics_list_.end();
        i++) {
     delete *i;