[test_runner] Migrate some test hooks to RenderFrameObserver

This CL migrates test hooks related to dumping frame loader callbacks
from overriding WebLocalFrameClient methods to using a
RenderFrameObserver.

This approach removes some test-only plumbing, and also allows for
refactoring of WebLocalFrameClient callbacks without affecting
a lot of tests as long as RenderFrameObserver API stays the same.

Drive-by: removed unused DidDetectXSS.

Bug: 855189
Change-Id: I8d28ed9ec211011b260a6cf0bc8ad7d45d60a37d
Reviewed-on: https://chromium-review.googlesource.com/c/1266722
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597960}
15 files changed