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

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

 // Copyright 2015 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.
 
 /**
  * @fileoverview Test suite for the Material Design history page.
  */
 
 var ROOT_PATH = '../../../../../';
 
@@ skipping 15 matching lines @@
   /** @override */
   runAccessibilityChecks: false,
 
   extraLibraries: PolymerTest.getLibraries(ROOT_PATH).concat([
     'test_util.js',
     'browser_service_test.js',
     'history_drawer_test.js',
     'history_grouped_list_test.js',
     'history_item_test.js',
     'history_list_test.js',
+    'history_metrics_test.js',
     'history_overflow_menu_test.js',
     'history_routing_test.js',
     'history_supervised_user_test.js',
     'history_synced_tabs_test.js',
     'history_toolbar_test.js'
   ]),
 
+  registerHistogramCallback_: function() {

[tsergeant, 2016/08/15 07:05:18]

I'm not a big fan of this:

Firstly, can it be local to the test, rather than applying to every test and
attaching results to window?

Secondly, since all you care about is the arguments passed to BrowserService, it
may be more appropriate to fake out the BrowserService instance and track the
calls in there.

[calamity, 2016/08/17 03:15:29]

Changed this as discussed

+    window.histogramMap = {};
+    registerMessageCallback(
+        'metricsHandler:recordInHistogram', this, function(args) {
+          if (!(args[0] in window.histogramMap))
+            window.histogramMap[args[0]] = {};
+
+          if (!(args[1] in window.histogramMap[args[0]]))
+            window.histogramMap[args[0]][args[1]] = 0;
+
+          window.histogramMap[args[0]][args[1]]++;
+        });
+  },
+
   /** @override */
   setUp: function() {
     PolymerTest.prototype.setUp.call(this);
 
     suiteSetup(function() {
+      this.registerHistogramCallback_();
       // Wait for the top-level app element to be upgraded.
       return waitForAppUpgrade().then(function() {
         $('history-app').queryState_.queryingDisabled = true;
 
         // Ensure the search bar is focused on load.
         assertTrue(
             $('history-app')
                 .$.toolbar.$['main-toolbar']
                 .getSearchField()
                 .isSearchFocused());
+
       });
-    });
+    }.bind(this));
   },
 };
 
 TEST_F('MaterialHistoryBrowserTest', 'BrowserServiceTest', function() {
   md_history.browser_service_test.registerTests();
   mocha.run();
 });
 
 TEST_F('MaterialHistoryBrowserTest', 'DrawerTest', function() {
   md_history.history_drawer_test.registerTests();
   mocha.run();
 });
 
 TEST_F('MaterialHistoryBrowserTest', 'HistoryGroupedListTest', function() {
   md_history.history_grouped_list_test.registerTests();
   mocha.run();
 });
 
 TEST_F('MaterialHistoryBrowserTest', 'HistoryItemTest', function() {
   md_history.history_item_test.registerTests();
   mocha.run();
 });
 
 TEST_F('MaterialHistoryBrowserTest', 'HistoryListTest', function() {
   md_history.history_list_test.registerTests();
   mocha.run();
 });
 
+TEST_F('MaterialHistoryBrowserTest', 'HistoryMetricsTest', function() {
+  md_history.history_metrics_test.registerTests();
+  mocha.run();
+});
+
 TEST_F('MaterialHistoryBrowserTest', 'HistoryToolbarTest', function() {
   md_history.history_toolbar_test.registerTests();
   mocha.run();
 });
 
 TEST_F('MaterialHistoryBrowserTest', 'HistoryOverflowMenuTest', function() {
   md_history.history_overflow_menu_test.registerTests();
   mocha.run();
 });
 
@@ skipping 50 matching lines @@
       return waitForAppUpgrade();
     });
   },
 };
 
 TEST_F('MaterialHistoryWithQueryParamTest', 'RoutingTestWithQueryParam',
   function() {
     md_history.history_routing_test_with_query_param.registerTests();
     mocha.run();
 });