Revert 228779 "Update defaults for InstantExtended."

Introduces crashes on the mac tests: http://build.chromium.org/p/chromium.mac/builders/Mac%2010.6%20Tests%20%28dbg%29%284%29/builds/34018/steps/unit_tests/logs/stdio

Specifically, these tests now crash:
  TabStripControllerTest.TabCloseDuringDrag
  TabposeWindowTest.TestModelObserver
  TabposeWindowTest.TestShow

And this test suite is referenced in this patch.

> Update defaults for InstantExtended.
> 
> Flip the InstantExtended New Tab page to on by default and remove the flags. 
> Add a separate flag to control query in the omnibox (which is still off by
> default).
> 
> Also fixes a ton of tests that needed adjusting for Instant Extended. Mostly
> the changes stem from the fact that we're prerendering the Instant Extended
> New Tab page which changes assumptions in a bunch of tests.
> 
> BUG=297915
> 
> Review URL: https://codereview.chromium.org/24733003

TBR=samarth@chromium.org

Review URL: https://codereview.chromium.org/27235010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228794 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228794