Pepper: add quota_amount and max_written_offset fields to SerializedHandle.
This field will be non-zero if the file is contained in a file system that
requires quota checks. This will be used by the NaCl PPAPI proxy to
verify that file writes respect quota.

The NaClQuotaAmount class is defined which is thread safe ref-counted, so
multiple file descriptors can modify quota amounts.

BUG=194304

Review URL: https://codereview.chromium.org/60733002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241691 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241691