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
diff --git a/drm/drmserver/DrmManagerService.cpp b/drm/drmserver/DrmManagerService.cpp
index 2600a2c..4b8b3f6 100644
--- a/drm/drmserver/DrmManagerService.cpp
+++ b/drm/drmserver/DrmManagerService.cpp
@@ -130,13 +130,14 @@
         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) {