Remove IMMS#MSG_START_HANDWRITING

This CL inlines

  InputMethodManagerService#MSG_START_HANDWRITING

handler as it has always been executed from the calling thread.

There should be no observable behavior change.

Bug: 215609403
Test: presubmit
Change-Id: Ia28f7ed55e59d9cfda98338a2a94550a6a477102
1 file changed