GitLab

Allow CastWebView to be created and WebContents retrieved so that a
WebContentsObserver can be added before navigating to the URL.

Bug: internal b/73180315
Test: cast_shell_internal_browsertests
Change-Id: I0c47b5f3c1dca4fe9384c6675b3edf6acd51c793
Reviewed-on: https://chromium-review.googlesource.com/923714Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: James West <jameswest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537493}