Created the dialog offering the user to merge their account data or keep it

chrome/android/java/AndroidManifest.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- 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. -->
 
 <!--
 Note: This is a jinja2 template, processed at build time into the final manifest.
 
 Blocks denoted with { % block some_name % }foo{ % endblock % } can be overridden
 by a child template that "extends" this file.
@@ skipping 244 matching lines @@
             android:theme="@style/MainTheme"
             android:autoRemoveFromRecents="true">
         </activity>
         <activity android:name="org.chromium.chrome.browser.firstrun.FirstRunActivity"
             android:theme="@style/DialogWhenLarge"
             android:label="@string/fre_label"
             android:launchMode="singleTop"
             android:windowSoftInputMode="stateHidden|adjustPan"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|mcc|mnc">
         </activity>
+        <activity android:name="org.chromium.chrome.browser.signin.AccountSigninActivity"
+          android:theme="@style/MainTheme"
+          android:launchMode = "singleInstance">

[newt (away), 2016/02/25 06:25:52]

Is singleInstance really what we want? This means that the activity will appear
in a new task (i.e. in recents it will appear as a separate item from the main
Chrome activity)

The docs for <activity> also warn: "singleTask and singleInstance — are not
appropriate for most applications, since they result in an interaction model
that is likely to be unfamiliar to users and is very different from most other
applications."

nit: remove spaces around =

[PEConn, 2016/02/25 14:19:51]

Done.

+        </activity>
         <activity android:name="org.chromium.chrome.browser.preferences.Preferences"
             android:theme="@style/PreferencesTheme"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|mcc|mnc"
             android:label="@string/preferences"
             android:exported="false">
         </activity>
         <activity android:name="org.chromium.chrome.browser.EmbedContentViewActivity"
             android:theme="@style/ThemeWithActionBar"
             android:hardwareAccelerated="false"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|mcc|mnc">
@@ skipping 449 matching lines @@
              choose the first MediaRouteController that can play it, so the order of the list can be important.
              The most specific MediaRouteControllers should be listed first, followed by more generic ones.
              The downstream manifest replaces this block, and hence replaces the list of media route
              controllers with its own list. -->
         <meta-data android:name="org.chromium.content.browser.REMOTE_MEDIA_PLAYERS"
             android:value="org.chromium.chrome.browser.media.remote.DefaultMediaRouteController"/>
 
         {% endblock %}
     </application>
 </manifest>