Don't compile Windows chrome_cleaner prompt code on other OSes

srt_chrome_prompt_impl.cc is code that is only used in Windows
but was compiled for all operating systems. Since it uses constants
that only exist in Windows it's kind of lucky that it doesn't
cause any problems, except in some jumbo build experiments where
there was linker errors.

(TBR for name change in BUILD.gn)
TBR=nparker@chromium.org

Bug: 904958
Change-Id: If1e3f76c7bc913d4041d0cb38b4891d898d24506
Reviewed-on: https://chromium-review.googlesource.com/c/1350870
Reviewed-by: Daniel Bratell <bratell@opera.com>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Joe Mason <joenotcharles@google.com>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#616067}
11 files changed