Allow WebState to load file:// URLs if virtual URL is app-specific.

Chrome for iOS allows loading PDF files from file system which were
received by external apps. Currently the feature is implemented with
ExternalFileController that uses separate WKWebView to load the file.

ExternalFileController is built on top of deprecated NativeContent API
which should be removed.

This CL allows WebState to load file URLs for browser-initiated
navigations that have app-specific virtual URL. This way external files
can be rendered in WebState onstead of using ExternalFileController.

Bug: 913602
Change-Id: I3453e367a8b57482ea01e4e97d24712bb976a8c0
Reviewed-on: https://chromium-review.googlesource.com/c/1401436
Reviewed-by: Ali Juma <ajuma@chromium.org>
Reviewed-by: Danyao Wang <danyao@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621754}
2 files changed