Allow only system signed apps to grant permissions at install

bug:20099946

Change-Id: Ifcc5c6638b4174ffb3ba452ae68a5a53b2d1ff0a
diff --git a/packages/Shell/AndroidManifest.xml b/packages/Shell/AndroidManifest.xml
index 9d16501..35e9636 100644
--- a/packages/Shell/AndroidManifest.xml
+++ b/packages/Shell/AndroidManifest.xml
@@ -93,6 +93,7 @@
     <uses-permission android:name="android.permission.BIND_APPWIDGET" />
     <uses-permission android:name="android.permission.UPDATE_APP_OPS_STATS" />
     <uses-permission android:name="android.permission.MODIFY_APPWIDGET_BIND_PERMISSIONS"/>
+    <uses-permission android:name="android.permission.INSTALL_GRANT_RUNTIME_PERMISSIONS" />
 
     <application android:label="@string/app_label">
         <provider