[Media Router] Add UMA histograms tracking component extension version/wakeups

chrome/browser/media/router/media_router_metrics_unittest.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/media/router/media_router_metrics.h"
+
+#include <limits.h>
+
+#include "base/version.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media_router {
+
+TEST(MediaRouteProviderMetricsTest, TestGetVersionDifference) {
+  base::Version second("50.0.2396.71");

[Wez, 2016/03/18 18:35:43]

nit: const base::Version kVersionForTest, say? - |second| doesn't seem a very
useful name here.

[mark a. foltz, 2016/03/18 20:11:00]

Done.

+  EXPECT_EQ(0, MediaRouterMetrics::GetVersionDifference(
+                   base::Version("50.0.2396.71"), second));
+  EXPECT_EQ(0, MediaRouterMetrics::GetVersionDifference(
+                   base::Version("50.0.2100.0"), second));
+  EXPECT_EQ(1, MediaRouterMetrics::GetVersionDifference(
+                   base::Version("51.0.2117.0"), second));
+  EXPECT_EQ(-1, MediaRouterMetrics::GetVersionDifference(
+                    base::Version("49.0.2138.0"), second));
+  EXPECT_EQ(-3, MediaRouterMetrics::GetVersionDifference(
+                    base::Version("47.0.1134.0"), second));
+  EXPECT_EQ(std::numeric_limits<int>::min(),
+            MediaRouterMetrics::GetVersionDifference(base::Version("blargh"),
+                                                     second));
+  EXPECT_EQ(
+      std::numeric_limits<int>::min(),
+      MediaRouterMetrics::GetVersionDifference(base::Version(""), second));
+  EXPECT_EQ(std::numeric_limits<int>::min(),
+            MediaRouterMetrics::GetVersionDifference(base::Version("-1.0.0.0"),
+                                                     second));
+  EXPECT_EQ(
+      std::numeric_limits<int>::min(),
+      MediaRouterMetrics::GetVersionDifference(base::Version("0"), second));
+}
+
+}  // namespace media_router