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This is the last of CRWWebDelegate methods used by CRWWebController, removing it
will allow deleting the CRWWebDelegate entirely.
Also removed it from Tab and from PreloadController which were implementing them.
The logic of handling external apps is now entirely moved to AppLauncherTabHelper
which is a policy decider and is attached to the web state used by the CRWWebController.

Bug: 850760, 681867, 674991
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I2df6282ae561eef2e1da8fac605f42dbfe4cb97b
Reviewed-on: https://chromium-review.googlesource.com/1124942
Commit-Queue: Mohammad Refaat <mrefaat@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Danyao Wang <danyao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578447}