Adding Priority field to cookies.

This CL focuses on cookie parser, CanonicalCookie, and making callers pass PRIORITY_DEFAULT where applicable.

What's NOT included in this CL:
- TODO(rogerm): Persistence in SQL database.
- TODO(huangs): Using cookie priority to affect cookie eviction.
- TODO(huangs): Make priorities available for extension API (right now default value is used to set).
- TODO(lower priority): Cookie viewer update.
- TODO(lower priority): WebCookie update in webkit/glue.

BUG=232693

Review URL: https://codereview.chromium.org/14113014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@195245 0039d316-1c4b-4281-b951-d872f2087c98
20 files changed