Set up font precaching in ppapi process

Without this GetOutlineTextMetrics fails in
third_party/skia/src/ports/SkFontHost_win.cpp resulting in garbage
font data being returned to Flash.

R=brettw@chromium.org, cpu@chromium.org
TBR=piman@chromium.org
BUG=308632

Review URL: https://codereview.chromium.org/118083004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241916 0039d316-1c4b-4281-b951-d872f2087c98
MessageLoop(TYPE_UI) -> MessageLoopForUI

Converts creation of MessageLoopForUI from MessageLoop(TYPE_UI) to
MessageLoopForUI.

This is a step in the direction of moving type out of MessageLoop.

BUG=none
TEST=none
R=darin@chromium.org

Review URL: https://codereview.chromium.org/108713004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241917 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241917