android: Add template to export sandboxed service

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 606 matching lines @@
         <!-- NOTE: If you change the value of "android:process" for the below services,
              you also need to update kHelperProcessExecutableName in chrome_constants.cc. -->
         {% set num_sandboxed_services = 20 %}
         <meta-data android:name="org.chromium.content.browser.NUM_SANDBOXED_SERVICES"
             android:value="{{ num_sandboxed_services }}"/>
         {% for i in range(num_sandboxed_services) %}
         <service android:name="org.chromium.content.app.SandboxedProcessService{{ i }}"
             android:process=":sandboxed_process{{ i }}"
             android:permission="{{ manifest_package }}.permission.CHILD_SERVICE"
             android:isolatedProcess="true"
-            android:exported="false" />
+            android:exported="{{sandboxed_service_exported|default(false)}}"
+            tools:ignore="ExportedService"

[mnaganov (inactive), 2016/01/26 18:25:50]

I guess this is only needed when the service is exported. But maybe it doesn't
harm when it's not.

[Robert Sesek, 2016/01/26 18:30:39]

It would be bad if android:exported="true" and andriod:externalService="false"
AND we were to turn on multiprocess. But if multiprocess is always going to have
externalService="true", then I think that's OK. Though it's probably safest, and
best for tooling, if the tools:ignore were wrapped in a condition gated on
externalService.

[boliu, 2016/01/26 18:58:03]

Couldn't figure out how to do jinja var with space in gn. So just wrapped the
tools:ignore part in an if instead.

+            {{sandboxed_service_extra_flags|default('')}} />
         {% endfor %}
 
         {% set num_privileged_services = 3 %}
         <meta-data android:name="org.chromium.content.browser.NUM_PRIVILEGED_SERVICES"
             android:value="{{ num_privileged_services }}"/>
         {% for i in range(num_privileged_services) %}
         {% set privileged_process_name = ':privileged_process%d' % i %}
         <!-- 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" />
@@ skipping 68 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>