[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() {
+  function registerTests() {
+    suite('Metrics', function() {
+      test('History.HistoryView', function() {
+        var app = $('history-app');
+        app.grouped_ = true;
+
+        var histogram = window.histogramMap['History.HistoryView'];
+        assertEquals(1, histogram[HistoryViewHistogram.HISTORY]);
+
+        app.selectedPage_ = 'syncedTabs';
+        return waitForAnimationFrame().then(() => {
+          assertEquals(1, histogram[HistoryViewHistogram.SIGNIN_PROMO]);
+          updateSignInState(true);
+          return waitForAnimationFrame();

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

waitForAnimationFrame is very specific. Does flush work? Do all of these need
it?

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

flush() doesn't seem to work. Since HistoryView is logged on the next animation
frame always, each of these does indeed need it =(

+        }).then(() => {
+          assertEquals(1, histogram[HistoryViewHistogram.SYNCED_TABS]);
+          app.selectedPage_ = 'history';
+          return waitForAnimationFrame();
+        }).then(() => {
+          assertEquals(2, histogram[HistoryViewHistogram.HISTORY]);
+          app.set('queryState_.range', HistoryRange.WEEK);
+          return waitForAnimationFrame();
+        }).then(() => {
+          assertEquals(1, histogram[HistoryViewHistogram.GROUPED_WEEK]);
+          app.set('queryState_.range', HistoryRange.MONTH);
+          return waitForAnimationFrame();
+        }).then(() => {
+          assertEquals(1, histogram[HistoryViewHistogram.GROUPED_MONTH]);
+        });
+      });
+    });
+  }
+  return {
+    registerTests: registerTests
+  };
+});