Added functions to WebDatabase and WebDataService for recording frequent entries in text input elements in forms. Also added the class AutofillManager which gets instantiated once per WebContents and provides an API from which the database can be easily accessed to provide a list of possible desired values to be entered in a text field given what the user has already typed there.

      Review URL: http://codereview.chromium.org/8845

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@4809 0039d316-1c4b-4281-b951-d872f2087c98