Another effort to fix WebRTC notification for Custom Tabs

Another effort to fix WebRTC notification for Custom Tabs

In https://codereview.chromium.org/1327193004, "Touch to return" was
removed from all normal chrome tabs, an it was added only to Custom
tabs. This is exactly the opposite behavior we expect.

This CL fixes the string mistake.

BUG=524855
Committed: https://crrev.com/e768e0cd80bd2f284a89ca476669de5cc145c105
Cr-Commit-Position: refs/heads/master@{#349296}

[Ian Wen, 2015-09-16 23:45:51]

ianwen@chromium.org changed reviewers:
+ dfalcantara@chromium.org

[Ian Wen, 2015-09-16 23:45:52]

Sorry to pester you again, Dan. 

（≧▼≦；)

[gone, 2015-09-16 23:47:48]

lgtm

[Ian Wen, 2015-09-16 23:49:21]

The CQ bit was checked by ianwen@chromium.org

[commit-bot: I haz the power, 2015-09-16 23:50:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1346403005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1346403005/1

[commit-bot: I haz the power, 2015-09-17 00:48:17]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-09-17 00:48:52]

Patchset 1 (id:??) landed as
https://crrev.com/e768e0cd80bd2f284a89ca476669de5cc145c105
Cr-Commit-Position: refs/heads/master@{#349296}