Add UMA metrics for multi-window mode and multi-instance

chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity2.java

 // 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.
 
 package org.chromium.chrome.browser;
 
+import org.chromium.base.metrics.RecordUserAction;
+
 /**
  * A subclass of ChromeTabbedActivity, used in Android N multi-window mode.
  *
  * This activity can appear side-by-side with ChromeTabbedActivity in multi-window mode. It has a
  * separate set of tabs, as determined by logic in TabWindowManager.
  *
  * Since ChromeTabbedActivity has launchMode="singleTask" in the manifest, there can't be two
  * instances of ChromeTabbedActivity; hence this activity is needed. Moreover, having separately-
  * named activities makes it possible to bring either existing activity to the foreground on the
  * desired side of the screen when firing an intent.
  */
-public class ChromeTabbedActivity2 extends ChromeTabbedActivity {}
+public class ChromeTabbedActivity2 extends ChromeTabbedActivity {
+    @Override
+    protected void onDeferredStartupForMultiWindowMode() {
+        RecordUserAction.record("Android.MultiWindowMode.MultiInstance.Enter");
+        recordMultiWindowModeScreenWidth();
+    }
+
+    @Override
+    protected void recordMultiWindowModeChangedUserAction(boolean isInMultiWindowMode) {
+        // Record separate user actions for entering/exiting multi-window mode to avoid recording
+        // the same action twice when two instances are running.
+        if (isInMultiWindowMode) {
+            RecordUserAction.record("Android.MultiWindowMode.Enter-SecondInstance");
+        } else {
+            RecordUserAction.record("Android.MultiWindowMode.Exit-SecondInstance");
+        }
+    }
+}