<webview>: Disable Chrome Extension URLs on Beta and Stable Channels

The API has not been finalized yet. Disable support for chrome-extension: URLs
on beta and stable channels until then.

BUG=313448
R=creis@chromium.org, kalman@chromium.org

Review URL: https://codereview.chromium.org/48043004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232123 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232123
Refactor RulesRegistryWithCache to RulesRegistry

As a prerequisites to isolating declarative RulesRegistry on a per-webview basis, we need to do some cleanup.

1. Get rid of the abstract class RulesRegistry, RulesRegistryWithCache becomes RulesRegistry. The caching component becomes an optional delegate.
2. Get rid of InitializingRulesRegistry. Move that functionality down into RulesRegistry.

This CL accomplishes the above but the RulesCacheDelegate is always installed. It will become optional in a subsequent CL.

BUG=312461
R=jyasskin@chromium.org, vabr@chromium.org

Review URL: https://codereview.chromium.org/49693003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232124 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232124