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/drm/libmediadrm/tests/EventMetric_test.cpp b/drm/libmediadrm/tests/EventMetric_test.cpp
new file mode 100644
index 0000000..eb6c4f6
--- /dev/null
+++ b/drm/libmediadrm/tests/EventMetric_test.cpp
@@ -0,0 +1,142 @@
+/*
+ * Copyright 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.
+ */
+
+#include <gtest/gtest.h>
+
+#include "EventMetric.h"
+
+namespace android {
+
+/**
+ * Unit tests for the EventMetric class.
+ */
+
+TEST(EventMetricTest, IntDataTypeEmpty) {
+  EventMetric<int> metric("MyMetricName", "MetricAttributeName");
+
+  std::map<int, EventStatistics> values;
+
+  metric.ExportValues(
+      [&] (int attribute_value, const EventStatistics& value) {
+          values[attribute_value] = value;
+      });
+
+  EXPECT_TRUE(values.empty());
+}
+
+TEST(EventMetricTest, IntDataType) {
+  EventMetric<int> metric("MyMetricName", "MetricAttributeName");
+
+  std::map<int, EventStatistics> values;
+
+  metric.Record(4, 7);
+  metric.Record(5, 8);
+  metric.Record(5, 8);
+  metric.Record(5, 8);
+  metric.Record(6, 8);
+  metric.Record(6, 8);
+  metric.Record(6, 8);
+
+  metric.ExportValues(
+      [&] (int attribute_value, const EventStatistics& value) {
+          values[attribute_value] = value;
+      });
+
+  ASSERT_EQ(2u, values.size());
+  EXPECT_EQ(4, values[7].min);
+  EXPECT_EQ(4, values[7].max);
+  EXPECT_EQ(4, values[7].mean);
+  EXPECT_EQ(1, values[7].count);
+
+  EXPECT_EQ(5, values[8].min);
+  EXPECT_EQ(6, values[8].max);
+  // This is an approximate value because of the technique we're using.
+  EXPECT_NEAR(5.5, values[8].mean, 0.2);
+  EXPECT_EQ(6, values[8].count);
+}
+
+TEST(EventMetricTest, StringDataType) {
+  EventMetric<std::string> metric("MyMetricName", "MetricAttributeName");
+
+  std::map<std::string, EventStatistics> values;
+
+  metric.Record(1, "a");
+  metric.Record(2, "b");
+  metric.Record(2, "b");
+  metric.Record(3, "b");
+  metric.Record(3, "b");
+
+  metric.ExportValues(
+      [&] (std::string attribute_value, const EventStatistics& value) {
+          values[attribute_value] = value;
+      });
+
+  ASSERT_EQ(2u, values.size());
+  EXPECT_EQ(1, values["a"].min);
+  EXPECT_EQ(1, values["a"].max);
+  EXPECT_EQ(1, values["a"].mean);
+  EXPECT_EQ(1, values["a"].count);
+
+  EXPECT_EQ(2, values["b"].min);
+  EXPECT_EQ(3, values["b"].max);
+  EXPECT_NEAR(2.5, values["b"].mean, 0.2);
+  EXPECT_EQ(4, values["b"].count);
+}
+
+// Helper class that allows us to mock the clock.
+template<typename AttributeType>
+class MockEventTimer : public EventTimer<AttributeType> {
+ public:
+  explicit MockEventTimer(nsecs_t time_delta_ns,
+                          EventMetric<AttributeType>* metric)
+      : EventTimer<AttributeType>(metric) {
+    // Pretend the event started earlier.
+    this->start_time_ = systemTime() - time_delta_ns;
+  }
+};
+
+TEST(EventTimerTest, IntDataType) {
+  EventMetric<int> metric("MyMetricName", "MetricAttributeName");
+
+  for (int i = 0; i < 5; i++) {
+    {
+      // Add a mock time delta.
+      MockEventTimer<int> metric_timer(i * 1000000, &metric);
+      metric_timer.SetAttribute(i % 2);
+    }
+  }
+
+  std::map<int, EventStatistics> values;
+  metric.ExportValues(
+      [&] (int attribute_value, const EventStatistics& value) {
+          values[attribute_value] = value;
+      });
+
+  ASSERT_EQ(2u, values.size());
+  EXPECT_LT(values[0].min, values[0].max);
+  EXPECT_GE(4000, values[0].max);
+  EXPECT_GT(values[0].mean, values[0].min);
+  EXPECT_LE(values[0].mean, values[0].max);
+  EXPECT_EQ(3, values[0].count);
+
+  EXPECT_LT(values[1].min, values[1].max);
+  EXPECT_GE(3000, values[1].max);
+  EXPECT_GT(values[1].mean, values[1].min);
+  EXPECT_LE(values[1].mean, values[1].max);
+  EXPECT_EQ(2, values[1].count);
+}
+
+}  // namespace android