Make step annotations on Windows to end with '\n' like on other platforms.
Make step annotations on Windows to end with '\n' like on other platforms.

Under some conditions successfully finished steps are marked as failed
by annotator on Windows (and only on Windows). This CL should fix that.

R=stip@chromium.org
BUG=358815

Review URL: https://codereview.chromium.org/272723004

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@269007 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build