Add methods to CompiledFileSystem that memoize returned
file system interfaces for processing API schemas and
Parse()ing JSON configuration data.

This should reduce cron time by preventing configuration
files from being parsed multiple times.

BUG=295812, 305280
NOTRY=true

Review URL: https://codereview.chromium.org/32513005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230160 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230160