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

This reverts commit 9137d7a25e1e1e1243511d74e8b4cbf7cb7d9ce3.

git-svn-id: svn://svn.chromium.org/blink/trunk@155114 bbb929c8-8fbe-4397-9dbb-9b2b20218538