[Subresource Filter] Add ability to index ruleset from resource bundle

This CL adds the ability for the subresource filter to index and
publish the ruleset from unindexed ruleset data stored as a resource in
the resource bundle. This functionality paves the way for WebLayer's
upcoming packaging of the in-repo unindexed ruleset data in the
resource bundle.

We also add a unittest of the new functionality. To facilitate adding
the unittest, we add the ability to mock out LoadDataResourceString()
to ui::ResourceBundle::Delegate and ui::MockResourceBundleDelegate.

TBR=spang@chromium.org

Bug: 1116095
Change-Id: Idb2c1b85465ab97e787c8191070f00acd571fadb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2516519


Commit-Queue: Colin Blundell <blundell@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824925}