Add EventMetric and a single use case.

Adds an EventMetric class, associated unit tests, and an instance of the
EventMetric to DrmHal. Also added a unit test for CounterMetric and
created a class to hold all of the future metric instances.

BUG: 64001676

Test: Added and ran unit tests.  Also added a CTS test case.
Change-Id: Ic94bedd5f8293a58a939613a4ae69ce656a772be
diff --git a/media/libmedia/include/media/DrmMetrics.h b/media/libmedia/include/media/DrmMetrics.h
new file mode 100644
index 0000000..f62c5f8
--- /dev/null
+++ b/media/libmedia/include/media/DrmMetrics.h
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef DRM_METRICS_H_
+#define DRM_METRICS_H_
+
+#include <media/CounterMetric.h>
+#include <media/EventMetric.h>
+
+namespace android {
+
+/**
+ * This class contains the definition of metrics captured within MediaDrm.
+ * It also contains a method for exporting all of the metrics to a
+ * MediaAnalyticsItem instance.
+ */
+class MediaDrmMetrics {
+ public:
+  explicit MediaDrmMetrics();
+  // Counter of times openSession was called.
+  CounterMetric<status_t> mOpenSessionCounter;
+  // Counter and timing of the getKeyRequest call.
+  EventMetric<status_t> mGetKeyRequestTiming;
+
+  // TODO: Add the full set of metrics to be captured.
+
+  // Export the metrics to a MediaAnalyticsItem.
+  void Export(MediaAnalyticsItem* item);
+};
+
+}  // namespace android
+
+#endif  // DRM_METRICS_H_