Add a commandline flag for TargetedStyleRecalc. Chromium side of change. Goes with crrev.com/149803002.

BUG=335247

Review URL: https://codereview.chromium.org/148883013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248023 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248023