Revert "Make Activites touch opaque - DO NOT MERGE"

This reverts commit 74ce78df.

Reason for revert: re-release due to functional regression

Change-Id: I71e2e889d1f2d026f708bdb617b73a5c7c10467d
(cherry picked from commit on googleplex-android-review.googlesource.com host: dd4ee687)
Merged-In: I71e2e889d1f2d026f708bdb617b73a5c7c10467d