Add extra definitions to <activity-alias> that targets ChromeTabbedActivity.

Bug: 845328
Change-Id: Ia55620022af7303904c3da0987f1514822d8c973
Reviewed-on: https://chromium-review.googlesource.com/1089865Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Charlie Ma <charliema@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565094}

chrome/android/java/AndroidManifest.xml

@@ -495,6 +495,9 @@ by a child template that "extends" this file.
             <meta-data android:name="android.app.shortcuts"
                 android:resource="@xml/launchershortcuts" />
             {{ self.supports_vr() }}
+            {% if min_sdk_version|int >= 21 %}
+            {{ self.extra_web_rendering_activity_definitions() }}
+            {% endif %}
         </activity-alias>
         <activity android:name="org.chromium.chrome.browser.ChromeTabbedActivity2"
             android:theme="@style/TabbedModeTheme"