Revert of Add --headless flag to Windows (patchset #29 id:560001 of https://codereview.chromium.org/2762593002/ )

Reason for revert:
Testing revert on --headless flag, due to increase in child_dll size: https://bugs.chromium.org/p/chromium/issues/detail?id=714841

Original issue's description:
> Launch bug: https://bugs.chromium.org/p/chromium/issues/detail?id=705916
>
> Add --headless flag to Windows:
>
> Fix browser_tests not compiling properly on windows
> Fix headless/BUILD.gn by:
>    - Changing headless_lib to a headless component, following steps in https://chromium.googlesource.com/chromium/src/+/master/docs/component_build.md and fixing the build for linux, since it now compiles as a shared_library when component build is true.
>    - Adding neccesary HEADLESS_EXPORT (submitted in https://codereview.chromium.org/2775693003/)
>    - Disabling breakpad in windows (will fix in a separate CL)
>
>
> BUG=686608
>
> Review-Url: https://codereview.chromium.org/2762593002
> Cr-Original-Commit-Position: refs/heads/master@{#466176}
> Committed: https://chromium.googlesource.com/chromium/src/+/e3c745d4b37a659afaa0358c7de7b9bc881decb5
> Review-Url: https://codereview.chromium.org/2762593002
> Cr-Commit-Position: refs/heads/master@{#466259}
> Committed: https://chromium.googlesource.com/chromium/src/+/d238dae172d63175b562f99fc988e47e5213a244

TBR=alexclarke@chromium.org,sky@chromium.org,skyostil@chromium.org,wfh@chromium.org,jzfeng@chromium.org,nick@chromium.org,hans@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=686608

Review-Url: https://codereview.chromium.org/2837093003
Cr-Commit-Position: refs/heads/master@{#466871}
22 files changed