Replace execInWindow with execInThread #6885
Replace nvdaHelperRemote's execInWindow with execInThread, which uses PostThreadMessage rather than PostMessage.
…sed in a text box in Mozilla applications." This changes execInWindow to again use PostMessage rather than SendMessageCallback. This reverts commit 657fb56.
… PostThreadMessage rather than PostMessage. This still allows us to execute code in a thread via the message queue (avoiding Gecko E10s issues with SendMessage) but also still fixes #6422 as the message will still be received even if the window is destroied.