Move decidePolicyForNavigationResponse to CRWWKNavigationHandler.

This CL moves WKNavigationDelegate.decidePolicyForNavigationResponse
from CRWWebController into CRWWKNavigationHandler.

Bug: 956511
Change-Id: I03be8af43fd644ef87fde6ef215098725ab1f33e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617491
Commit-Queue: Yi Su <mrsuyi@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661304}
3 files changed