Refactoring web_test
Split WebTestBase into WebTest and WebTestBase.
WebTest is used as a test fixture in web tests that don't
need a WebController but need other necessary pieces such as
WebThreads, WebClient etc.
As a proof of concept changed ActiveStateManagerImplTest,
BrowsingDataStoreTest to use WebTest.
As a result, a lot of code duplication is eliminated.
A lot of boilerplate (need to run web unittests) is now present
in WebTest.
BUG=480507
Review URL: https://codereview.chromium.org/
1246103008
Cr-Commit-Position: refs/heads/master@{#340327}