Currently, NavigationThrottles attach only when a URLRequest will be
created, allowing throttles to participate in the network request
portion of a navigation. However, for navigations that will immedaitely
commit because no URLRequest is needed, it is impossible to throttle
the navigation. Navigations that immediately commit include
about:blank, about:srcdoc, and most* (see below) same document
navigations.
This CL introduces a new NavigationThrottle callback,
WillCommitWithoutUrlLoader. WillCommitWithoutUrlLoader is called only
in the immediate commit case (when no other NavigationThrottle
callbacks will be called), and allows the NavigationThrottle to defer
or cancel the navigation, as any other callback does.
Currently, no NavigationThrottles use WillCommitWithoutUrlLoader, but
it will be used by a new throttle that will be introduced in
https://chromium-review.googlesource.com/c/chromium/src/+/4092862.
* Some same document navigations are committed synchronously in the
renderer process, and the browser process is only told about the navigation after the fact, so we can't throttle them. Those
navigations are renderer-initiated non-back-forward same-document
navigations. WillCommitWithoutUrlLoader can intercept all
browser-initiated same-document navigations, as well as
renderer-initiated back-forward same-document navigations.
Bug: 1067613, 1371580
Change-Id: I7066e69bee5e891c9aec1b79c8c266e011f726ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4210858
Commit-Queue: Nate Chapin <japhet@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1102862}
