Android denial of service attack using class 0 SMS messages

Bug 9702645
Bug 11970403 - Change to ClassZeroActivity to singleTask

Cherry pick the change from master.

Making every AlertDialog immediately visible can lead to exhaustion
of graphics-related resources, typically memory, resulting in a
broken bufferqueue/hw renderer, and subsequent system crash.

Make ClassZeroActivity a singleTask activity, and queue incoming
messages if one is already being displayed.

Change-Id: I0aef7b857364acc404e79581ba5e503571065483
Revert "ClassZeroActivity: Resolve some possible NPEs, and refactor common code"

This reverts commit 3f65c4e575d33ddeb5bd547bfffb094af5c61894.
Revert "ClassZeroActivity: Queue messages instead of displaying them all at once"

This reverts commit 6c4c0e3046cfb74b8c7d4a049e29ad41831a5062.
Revert "ClassZeroActivity: Holo it"

This reverts commit e521bde98fa0d552d105f2829a3223ec62760152.
Merge remote-tracking branch 'aosp/kitkat-mr1-release' into HEAD