InstantExtended: Hide blank query page off NTP.

InstantExtended: Hide blank query page off NTP.

Otherwise we show a Google logo and identity on third-party websites
when the user backspaces away the query.

BUG=


Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=170758

[Jered, 2012-11-29 23:15:23]

Please review.

This is the last piece needed to make the overlay behave sanely on general
websites.

[sreeram, 2012-11-30 19:03:31]

So I just realized that InstantController::Show() doesn't actually enforce these
rules. I.e., even though we Hide() the preview for a variety of reasons in
Update() and elsewhere, as long as the search_mode_ is search_suggestions, the
preview can still call Show() and succeed. This could result in jank.

For example:
1. Type a partial query in tab A.
2. Switch to Tab B.
3. Do these quickly: Type "q" and Ctrl-T to switch to Tab A.
I'd expect that the page will call Show() and succeed. (Caveat: I haven't
actually tested it.)

If you don't want to take a stab at it in this CL, please file a new bug; I'll
LGTM this CL.

[commit-bot: I haz the power, 2012-11-30 21:51:24]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jered@chromium.org/11308284/1

[commit-bot: I haz the power, 2012-12-01 00:09:22]

Retried try job too often on win_rel for step(s) content_browsertests

[commit-bot: I haz the power, 2012-12-03 16:19:32]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jered@chromium.org/11308284/1

[commit-bot: I haz the power, 2012-12-03 17:07:59]

Retried try job too often on linux_rel for step(s) ash_unittests

[commit-bot: I haz the power, 2012-12-03 17:19:02]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jered@chromium.org/11308284/1

[commit-bot: I haz the power, 2012-12-03 18:02:42]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jered@chromium.org/11308284/1

[commit-bot: I haz the power, 2012-12-03 18:14:16]

Change committed as 170758