Allow WebStateObserver to observe N WebStates [47/N].

Convert CRWWebUIManager to directly track the registration
with the observed WebState instead of relying on deprecated
code in WebStateObserverBridge.

Bug: 775684
Change-Id: I7b6208672cb7340cd3f96ba3e127401f41f30771
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Reviewed-on: https://chromium-review.googlesource.com/778885
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518908}
1 file changed