Refactor setInputWindows

The logic for the actual window update is now factored out into a
separate function.
Otherwise, setInputWindows was too long and tough to reason about.
There should be no functional change in this CL.

Bug: none
Test: atest -a inputflinger_tests
Change-Id: I49c2eda5178de79de23f772ffc279249ca4402e8
2 files changed