[Media Router] Fix regression with icon not turning blue after casting.

[Media Router] Fix regression with icon not turning blue after casting.

Previously MR relies on the behavior of route response returning a
local displayable route on success. This is no longer the case, thus
the logic to turn the toolbar icon blue is no longer getting triggered.

The fix is to have the toolbar observe route list directly for local
displayable routes. Route queries have a much lower overhead than
before.

In a separate patch we will clean up the now obsolete
LocalMediaRoutesObserver API from MR and MR extension.

BUG=582278
Review URL: https://codereview.chromium.org/1648713004

Cr-Commit-Position: refs/heads/master@{#372750}
(cherry picked from commit 7f297c082c6be8d8495c5b4fe22069e93ed92a73)

Committed: https://chromium.googlesource.com/chromium/src/+/1fb5ee6a720f4480cfe013fd60b5f48cf46d7de3

[imcheng, 2016-02-02 20:26:50]

Description was changed from

==========
[Media Router] Fix regression with icon not turning blue after casting.

Previously MR relies on the behavior of route response returning a
local displayable route on success. This is no longer the case, thus
the logic to turn the toolbar icon blue is no longer getting triggered.

The fix is to have the toolbar observe route list directly for local
displayable routes. Route queries have a much lower overhead than
before.

In a separate patch we will clean up the now obsolete
LocalMediaRoutesObserver API from MR and MR extension.

BUG=582278

Review URL: https://codereview.chromium.org/1648713004

Cr-Commit-Position: refs/heads/master@{#372750}
(cherry picked from commit 7f297c082c6be8d8495c5b4fe22069e93ed92a73)
==========

to

==========
[Media Router] Fix regression with icon not turning blue after casting.

Previously MR relies on the behavior of route response returning a
local displayable route on success. This is no longer the case, thus
the logic to turn the toolbar icon blue is no longer getting triggered.

The fix is to have the toolbar observe route list directly for local
displayable routes. Route queries have a much lower overhead than
before.

In a separate patch we will clean up the now obsolete
LocalMediaRoutesObserver API from MR and MR extension.

BUG=582278

Review URL: https://codereview.chromium.org/1648713004

Cr-Commit-Position: refs/heads/master@{#372750}
(cherry picked from commit 7f297c082c6be8d8495c5b4fe22069e93ed92a73)

Committed:
https://chromium.googlesource.com/chromium/src/+/1fb5ee6a720f4480cfe013fd60b5...
==========

[imcheng, 2016-02-02 20:26:51]

Committed patchset #1 (id:1) manually as
1fb5ee6a720f4480cfe013fd60b5f48cf46d7de3.