WindowInputTests: assert in the test thread

WindowInputTests#testInjectFromThread has one assertion in the thread
started by the executor. When the assertion failure is thrown in the
executor-started thread, the call stack does not indicate which test
case is failing. Change the location of throwing the failure to make
sure assertion failure is thrown in the test thread, so that it is clear
which test is failing.

Bug: 202773778
Test: atest WindowInputTests
Change-Id: I167bab896df5c7e4754954e41aa390a9e61f1870
1 file changed