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WebLayer does not use //components/history and does not want to take a
dep on the (large) component, as every dep that WebLayer adds has an
impact on WebView. SubresourceFilterContentSettingsManager, however,
currently depends on //components/history for its optional observance of
the user's deletion of URLs from history.

This CL abstracts that dependency via the following changes:
- Adds the ability for SubresourceFilterProfileContext to store opaque
  embedder data (via a simple
  SubresourceFilterProfileContext::EmbedderData interface)
- Moves the history observance to a new SubresourceFilterHistoryObserver
  class that is an EmbedderData and takes in a
  SubresourceFilterContentSettingsManager instance to call into
- Has SubresourceFilterProfileContextFactory create
  SubresourceFilterHistoryObserver instances to be stored by
  SubresourceFilterProfileContext instances

In this way, WebLayer will be able to use
SubresourceFilterProfileContext, AdsInterventionManager, and
SubresourceFilterContentSettingsManager without taking on the
//components/history dep.

Bug: 1116095
Change-Id: Ic81f63447f10afef1c4946ca7751d810d0a9cbbb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2466761Reviewed-by: Eric Robinson <ericrobinson@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817020}