DrmManager: locally aggregate API metrics

Aggregate DrmManager API invocation counts per plugin over at least
fixed period of time before sending metrics to mediametrics service.

The default period is 1 day; the period is configurable through the
property drmmanager.metrics.period.

Bug: 134789967
Test: dumpsys media.metrics
Change-Id: I2cf28f1dfaa485ca319360705b872eed995b3d7f

drm/drmserver/DrmManagerService.cpp

@@ -130,13 +130,14 @@ DrmManagerService::DrmManagerService() :
         mDrmManager(NULL) {
     ALOGV("created");
     mDrmManager = new DrmManager();
+    mDrmManager->initMetricsLooper();
     mDrmManager->loadPlugIns();
 }
 
 DrmManagerService::~DrmManagerService() {
     ALOGV("Destroyed");
     mDrmManager->unloadPlugIns();
-    delete mDrmManager; mDrmManager = NULL;
+    mDrmManager = NULL;
 }
 
 int DrmManagerService::addUniqueId(bool isNative) {