Properly handle changes in phone audio focus.

Change-Id: I921651684f4369a47aa83e93010266c40be71a41
frameworks/base: Fix to avoid crash when the tab is not set from app

As the current tab is not set from application, getChildTabViewAt
returns Null value. Added a condition which checks whether mSelectTab
is set to first Tab.

(cherry picked from commit 9be6755efb149b22c36aa3eb7cc4ffe7e765e08a)

Change-Id: I11c77ca96333e2663d28db1b5fdb46602bd9e745
CRs-Fixed: 321176
Framework: Fix button label toasts when layout is RTL

Google have decided to set their gravity "relatively", while they measure only from the left.
The result? Toasts appearing in the wrong side of the screen.

Change-Id: If5e9d5fc2751fbef3eb058b241168fb9d8bf4b98