Create two new metric types to simplify metrics.

This is part one of a mult-part change to revise some metrics. Several
metrics are currently EventMetric type when they should be a simpler
type.

Test: Added unit tests for the new types. Also, re-ran existing tests.
Verified playback works with Google Play, and re-ran Widevine GTS tests.

Bug: 36220619
Change-Id: I2ec8fc355f66ad4834dd722aacd22541fb9c94ad

tests/Android.mk

@@ -12,10 +12,11 @@ WIDEVINE_TEST_MAKE_TARGETS := \
     cdm_engine_test \
     cdm_extended_duration_test \
     cdm_session_unittest \
+    counter_metric_unittest \
     crypto_session_unittest \
     device_files_unittest \
-    distribution_test \
-    event_metric_test \
+    distribution_unittest \
+    event_metric_unittest \
     file_store_unittest \
     file_utils_unittest \
     http_socket_test \
@@ -35,6 +36,7 @@ WIDEVINE_TEST_MAKE_TARGETS := \
     service_certificate_unittest \
     timer_unittest \
     usage_table_header_unittest \
+    value_metric_unittest \
     CastSignAPITest \
     MediaDrmAPITest \