Make the Pepper proxy support in-process font rendering.

This implements a WebKit thread in the PPAPI plugin process so we can do the
font calls without IPC. The existing font support was refactored into
a virtual class (to prevent PPAPI from depending on WebKit and creating a
circular GYP dependency).

This moves the renderer sandbox support into content/common so that it can
be used by the PPAPI process.
Review URL: http://codereview.chromium.org/6981001

git-svn-id: http://src.chromium.org/svn/trunk/src/build@84856 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

all.gyp

@@ -22,6 +22,7 @@
         '../media/media.gyp:*',
         '../net/net.gyp:*',
         '../ppapi/ppapi.gyp:*',
+        '../ppapi/ppapi_internal.gyp:*',
         '../printing/printing.gyp:*',
         '../sdch/sdch.gyp:*',
         '../skia/skia.gyp:*',