[FileAPI] Add QuotaReservationManager and related classes.

 * Adding QuotaReservationManager.
 * Adding Reservation, ReservationPool, OpenFile, ActiveFile as its inner class.

TEST=content_unittests:QuotaReservationManagerTest.*
BUG=303443
TBR=avi
NOTRY=true

Review URL: https://codereview.chromium.org/43323002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233199 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233199
Update licensecheck.pl for third_party/mach_override as of r233175.

BUG=315397
R=thestig@chromium.org

Review URL: https://codereview.chromium.org/60293005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233200 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233200