Revert "Remove InputMethodManagerService#mCaller" This reverts commit 7c46dc83efe879304dde3cadd105d0b96547e73d. Reason for revert: Droidfood blocking bug: 216588046 Bug: 192412909 Bug: 216588046 Change-Id: I12902c08d21d851a13ef7319f87e5dc784182228 (cherry picked from commit cc0498759b0e752d73d0551afa33ed9675d6e445) Merged-In:I12902c08d21d851a13ef7319f87e5dc784182228