renderer/platform/ cannot depend on Blink's core classes. This CL makes
`KeySystemConfigSelector::WebLocalFrameDelegate` a virtual class and
moves the creation of the WebLocalFrame to a subclass in `MediaFactory`.
Bug: 40760651
Change-Id: If20360e178ae631bee73f9ca39c6c530edd2ef5c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6377065
Commit-Queue: Henrique Ferreiro <hferreiro@igalia.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1438630}