Pages from other devices open in current tab.

* Opening a foreign session or recently closed now takes over the tab 
(nuking its navigation history)
* Opening a chrome-to-mobile page now loads in the current tab.

BUG=257102

Review URL: https://codereview.chromium.org/36473002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234684 0039d316-1c4b-4281-b951-d872f2087c98
Propagates the search result of start page to the app-list search box.

BUG=313899
R=xiyuan@chromium.org
TEST=manually

Review URL: https://codereview.chromium.org/55433002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234685 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234684
SVN changes up to revision 234685