Bug 1315201: Add license header to bottomsheet. r=sebastian

MozReview-Commit-ID: Iaafq67csMV

--HG--
extra : rebase_source : 804e1fbb6c8da9a0eca697dc149b41b836918d38

mobile/android/app/src/main/res/layout/activity_stream_contextmenu_bottomsheet.xml

@@ -1,4 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
 <LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"