Add support for getMetrics to IDrm

Adds support for the new getMetrics call to the IDrm interface and the
DrmHal implementation. The implementation currently returns a dummy
metric collection. Follow-up CLs will flesh out the implementation.

Bug: 64001676

Test: Ran the new unit test created in a related CL; ran Google Play.
Change-Id: Ia6a3af5b59a30ca55267f7e3ba278a510fc8c81e
diff --git a/drm/libmediadrm/DrmHal.cpp b/drm/libmediadrm/DrmHal.cpp
index bc37557..31344c3 100644
--- a/drm/libmediadrm/DrmHal.cpp
+++ b/drm/libmediadrm/DrmHal.cpp
@@ -838,6 +838,11 @@
     return toStatusT(status);
 }
 
+status_t DrmHal::getMetrics(MediaAnalyticsItem* metrics) {
+    // TODO: Replace this with real metrics.
+    metrics->setCString("/drm/mediadrm/dummymetric", "dummy");
+    return OK;
+}
 
 status_t DrmHal::setCipherAlgorithm(Vector<uint8_t> const &sessionId,
                                  String8 const &algorithm) {
@@ -1030,6 +1035,7 @@
     }
 }
 
+
 void DrmHal::reportMetrics() const
 {
     Vector<uint8_t> metrics;