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.


Review URL:

git-svn-id: svn:// 0039d316-1c4b-4281-b951-d872f2087c98
20 files changed