Eliminate AutofillWebDataService::FromBrowserContext().

Core code in the Autofill component now gets the AutofillWebDataService from
the embedder. This CL eliminates the declaration of the static
AutofillWebDataService::FromBrowserContext() from the Autofill component's core
code, instead having the concept of getting an AutofillWebDataService from a
BrowserContext/Profile be entirely an embedder-level concept.

BUG=303048

Review URL: https://codereview.chromium.org/72613006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238389 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238389