Ensure that WebFramesManager->GetMainWebFrame() always returns a valid WebFrame.

Remove extraneous |removeAllWebFrames| call to ensure a WebFrame exists for the main frame when navigating back then forward on a same page (ex:example.com#link) link.

Additionally, add tests to validate the returned WebFrame object.

Bug: 913825
Change-Id: I5abe3a50769564c1c95157eb713ee435093cbab4
Reviewed-on: https://chromium-review.googlesource.com/c/1368768
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616004}
2 files changed