Bug 1146735 - Change outer container to FrameLayout. r=liuche

--HG--
extra : commitid : 7xF6a73qIia
extra : rebase_source : 35d890aeb04caa28015487d9cc130ff5b7f2ce46

mobile/android/base/resources/layout/anchored_popup.xml

@@ -3,7 +3,7 @@
    - 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"
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
               android:background="@drawable/dropshadow"
@@ -22,4 +22,4 @@
                                                       android:orientation="vertical"/>
 
     </ScrollView>
-</LinearLayout>
+</FrameLayout>