[chromecast] MediaBlock: Added cast renderer initialization block.

Allowed a new type of media block that blocks cast_renderer
initialization instead of webmediaplayer loading.

Test: Manual test blocking is happening at the renderer by inspecting
device logs
Bug: b/134961542

Change-Id: I97b0e59a6752c43d14b8e96327079aa8669b1c00
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1673829
Reviewed-by: Sean Topping <seantopping@chromium.org>
Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Auto-Submit: Andres Medina <medinaandres@chromium.org>
Commit-Queue: Andres Medina <medinaandres@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672687}
12 files changed