Since this flag does not do any check during start input,
CL[1] removes this flag and the related parameter for IMM#onPostWindowFocus
to keep the logic simpler (included removing
ViewRootImpl#mHasHadWindowFocus).
Also remove this flag's debug string for For MultiClientInputMethod.
This is refector CL and does not impact any behavior change.
CL[1]: I9119f4846cbbd2b15246dea9a3b1fc5845dce951
Bug: 141738570
Test: Refector CL, make sure all existing test passed.
Change-Id: I9c8c9ac0ce5d0e4a803842d4cefb9119ec51024d
eac77301f8