Introduce background Download process to android

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 624 matching lines @@
         <!-- TODO(tedchoc): Omit this for release builds as MultiDex is debug only. --> 
         <meta-data android:name="{{ manifest_package }}{{ privileged_process_name }}.ignore_multidex"
 android:value="true" />
         <service android:name="org.chromium.content.app.PrivilegedProcessService{{ i }}"
             android:process="{{ privileged_process_name }}"
             android:permission="{{ manifest_package }}.permission.CHILD_SERVICE"
             android:isolatedProcess="false"
             android:exported="false" />
         {% endfor %}
 
+        <!-- Background download process, it may outlive chrome if download does not finish
+             when user kills chrome -->

[asanka, 2016/01/25 16:44:50]

Is this comment accurate? And if so, was there consensus that the download
process would outlive the browser process in the case where the user explicitly
kills the app (as opposed to Chrome being killed due to other reasons)?

I'm okay if that was the decision, but I want to make sure we are not violating
platform norms or user expectations.

[qinmin, 2016/01/25 22:48:23]

I think this should be the use case and should be expected by user, we can
confirm it with Sidv and Grace. 
The current behavior with Android DownloadManager is that when user explicitly
killing chrome, the download will continue. And we should match that behavior.

+        <service android:name="org.chromium.content.app.DownloadProcessService"
+            android:exported="false"
+            android:permission="{{ manifest_package }}.permission.CHILD_SERVICE"

[asanka, 2016/01/25 16:44:50]

Should this be left unset? What protections do we get from setting this to
CHILD_SERVICE?

Note that we want to restrict all other processes other than the browser process
from binding to this.

[qinmin, 2016/01/25 22:48:23]

This specifies that only processes with CHILD_SERVICE permission can start this
service, which means other apps cannot launch this. Since the GPU and renderer
process will or is already isolated process, they don't have any permissions,
and will not be able to bind or start this service

+            android:process=":download"/>

[svaldez, 2016/01/25 15:33:43]

nit: Reorder to match ordering of previous service definitions:

service android:name=... android:process=... android permission=...
android:isolatedProcess=... android:exported=...

[qinmin, 2016/01/25 22:48:23]

Done.

+
         <receiver android:name="org.chromium.chrome.browser.download.DownloadBroadcastReceiver"
             android:exported="false">
             <intent-filter>
                 <action android:name="android.intent.action.DOWNLOAD_NOTIFICATION_CLICKED"/>
             </intent-filter>
         </receiver>
 
         <receiver android:name="org.chromium.base.PowerStatusReceiver">
             <intent-filter>
                 <action android:name="android.intent.action.ACTION_POWER_CONNECTED"/>
@@ skipping 51 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>