Add CounterMetric and a single use case.

This adds a new class CounterMetric which is used to hold metric
information.  It also adds a single use case for recording and
reporting a counter metric.

BUG: 64001676

Test: Added and ran a new test for the specific CounterMetric use case.
Change-Id: I39cab8328f135e579f80b6c2fab721da5f569795
diff --git a/drm/libmediadrm/tests/Android.bp b/drm/libmediadrm/tests/Android.bp
new file mode 100644
index 0000000..674d3eb
--- /dev/null
+++ b/drm/libmediadrm/tests/Android.bp
@@ -0,0 +1,12 @@
+// Build definitions for unit tests.
+
+cc_test {
+    name: "CounterMetric_test",
+    srcs: ["CounterMetric_test.cpp"],
+    shared_libs: ["libmediadrm"],
+    include_dirs: ["frameworks/av/include/media"],
+    cflags: [
+      "-Werror",
+      "-Wall",
+    ],
+}