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

libwvdrmengine/cdm/metrics/test/distribution_unittest.cpp

@@ -0,0 +1,47 @@
+// Copyright 2017 Google Inc. All Rights Reserved.
+//
+// Unit tests for Distribution.
+
+#include <float.h>
+
+#include "distribution.h"
+
+#include "gtest/gtest.h"
+
+namespace wvcdm {
+namespace metrics {
+
+TEST(DistributionTest, NoValuesRecorded) {
+  Distribution distribution;
+  EXPECT_EQ(DBL_MAX, distribution.Min());
+  EXPECT_EQ(-DBL_MAX, distribution.Max());
+  EXPECT_EQ(0, distribution.Mean());
+  EXPECT_EQ(0, distribution.Count());
+  EXPECT_EQ(0, distribution.Variance());
+}
+
+TEST(DistributionTest, OneValueRecorded) {
+  Distribution distribution;
+  distribution.Record(5.0);
+  EXPECT_EQ(5, distribution.Min());
+  EXPECT_EQ(5, distribution.Max());
+  EXPECT_EQ(5, distribution.Mean());
+  EXPECT_EQ(1, distribution.Count());
+  EXPECT_EQ(0, distribution.Variance());
+}
+
+TEST(DistributionTest, MultipleValuesRecorded) {
+  Distribution distribution;
+  distribution.Record(5.0);
+  distribution.Record(10.0);
+  distribution.Record(15.0);
+  EXPECT_EQ(5, distribution.Min());
+  EXPECT_EQ(15, distribution.Max());
+  EXPECT_EQ(10, distribution.Mean());
+  EXPECT_EQ(3, distribution.Count());
+  EXPECT_NEAR(16.6667, distribution.Variance(), 0.0001);
+}
+
+}  // namespace metrics
+}  // namespace wvcdm
+