[Harmony Cast Dialog] Notify the component extension of dialog config

Notify the component extension whether WebUI or Views Cast dialog is
being used. The extension will log this info.

Move the ShouldUseViewsDialog() method from
media_router_dialog_controller_views.cc to media_router_feature.h.

b/111209425

Change-Id: I671f330088bfe959df487cd8b7947225940692d8
Reviewed-on: https://chromium-review.googlesource.com/1134186
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Derek Cheng <imcheng@chromium.org>
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575727}
6 files changed