[MD History] Add UMA stats for switching views and the CBD button.

chrome/test/data/webui/md_history/history_metrics_test.js

+// 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.
+
+cr.define('md_history.history_metrics_test', function() {
+  /**
+   * @constructor
+   * @extends {md_history.BrowserService}
+   */
+  var TestMetricsBrowserService = function() { this.histogramMap = {}; };
+
+  function registerTests() {
+    suite('Metrics', function() {
+      var service;
+      var app;
+
+      suiteSetup(function() {
+        TestMetricsBrowserService.prototype = {
+          __proto__: md_history.BrowserService.prototype,
+
+          /** @override */
+          recordHistogram: function(histogram, value, max) {
+            assertTrue(value < max);
+
+            if (!(histogram in this.histogramMap))
+              this.histogramMap[histogram] = {};
+
+            if (!(value in this.histogramMap[histogram]))
+              this.histogramMap[histogram][value] = 0;
+
+            this.histogramMap[histogram][value]++;
+          }
+        };
+      });
+
+      setup(function() {
+        md_history.BrowserService.instance_ = new TestMetricsBrowserService();
+        service = md_history.BrowserService.getInstance();
+
+        app = replaceApp();
+        return flush();
+      });
+
+      test('History.HistoryView', function() {
+        app.grouped_ = true;
+
+        var histogram = service.histogramMap['History.HistoryView'];
+        assertEquals(1, histogram[HistoryViewHistogram.HISTORY]);
+
+        app.selectedPage_ = 'syncedTabs';
+        assertEquals(1, histogram[HistoryViewHistogram.SIGNIN_PROMO]);
+        updateSignInState(true);
+        return flush().then(() => {
+          assertEquals(1, histogram[HistoryViewHistogram.SYNCED_TABS]);
+          app.selectedPage_ = 'history';
+          assertEquals(2, histogram[HistoryViewHistogram.HISTORY]);
+          app.set('queryState_.range', HistoryRange.WEEK);
+          assertEquals(1, histogram[HistoryViewHistogram.GROUPED_WEEK]);
+          app.set('queryState_.range', HistoryRange.MONTH);
+          assertEquals(1, histogram[HistoryViewHistogram.GROUPED_MONTH]);
+        });
+      });
+    });
+  }
+  return {
+    registerTests: registerTests
+  };
+});