Use different icons for the overlay and non-overlay cast buttons

Use different icons for the overlay and non-overlay cast buttons

We want the overlay cast icon to be visible on all backgrounds, so its
background has to be at least semi-opaque. The non-overlay cast icon,
however, should have the same background as the media controls, which
is easiest to achive by making its background transparent. As such we
need different icons for the two cases.

This CL simply provides the new icons. The corresponding Blink CL, which
uses them, is https://codereview.chromium.org/716613002.

BUG=426373
Committed: https://crrev.com/bea7c9b7f0a387378fd2756430712e6042ce2c2c
Cr-Commit-Position: refs/heads/master@{#303620}

[aberent, 2014-11-10 18:09:43]

aberent@chromium.org changed reviewers:
+ jam@chromium.org

[jam, 2014-11-11 04:27:11]

lgtm

[aberent, 2014-11-11 08:57:15]

The CQ bit was checked by aberent@chromium.org

[commit-bot: I haz the power, 2014-11-11 08:57:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/711083002/1

[commit-bot: I haz the power, 2014-11-11 09:47:50]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-11 09:48:35]

Patchset 1 (id:??) landed as
https://crrev.com/bea7c9b7f0a387378fd2756430712e6042ce2c2c
Cr-Commit-Position: refs/heads/master@{#303620}