Revert "Move WinPrecompile out of Source/WebKit/chromium"

This reverts commit 092d3bcaa5856aaa8a17109aec4347164a018568.

This CL is frustrating because all the try servers pass but the main waterfall
fails...

git-svn-id: svn://svn.chromium.org/blink/trunk@155256 bbb929c8-8fbe-4397-9dbb-9b2b20218538