Avoid the ifdef OS(WIN) in ClipboardUtilities.cpp.

Move the implementation of replaceNewlinesWithWindowsStyleNewlines() over
ClipboardUtilitiesWin.cpp.

BUG=None
TEST=None, no functional changes.
R=thakis@chromium.org

Review URL: https://codereview.chromium.org/26412004

git-svn-id: svn://svn.chromium.org/blink/trunk@159670 bbb929c8-8fbe-4397-9dbb-9b2b20218538