Show Cast dialog for browser-less windows

This CL enables anchoring the Cast dialog to gfx::Rect, so that a window
without a Browser object (e.g. CrOS video player) can show the dialog
anchored to it.

Bug: 930606
Change-Id: I107e27565970d2e7df68395b982ba1f9ff66b868
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1519469
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643405}
5 files changed