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The dialog tests are all removed because Media Router is switching to a new UI.
There are also a number of code refactoring because of this change.

Change-Id: I9bede536041e104d727fadac81089e47013711d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1437273
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: Charlie Andrews <charliea@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642671}