Refactored extension privilege enumeration and implemented URLPattern comparisons.

      This will allow checks on per origin extension resource access. Added origin
check when loading extension resources. 

BUG=45876
TEST=ExtensionTest.IsPrivilegeIncrease 
TEST=ExtensionTest.EffectiveHostPermissions
TEST=ExtensionBrowserTest.OriginPrivileges

Review URL: http://codereview.chromium.org/2808051

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@55103 0039d316-1c4b-4281-b951-d872f2087c98