Fix and re-enable RenderTextTest.Multiline_NormalWidth on XP

BUG=248597
TBR=asvitkine@chromium.org

Review URL: https://codereview.chromium.org/26358015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228344 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228344