Search providers extension API settings UI.

Add more info to the bubble shown on the settings page when extension take over a preference.

BUG=306128

Review URL: https://codereview.chromium.org/43013002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233976 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233976
Move FeatureSwitch to top-level extensions/

Move FeatureSwitch to extensions/common/
Move the switches used in FeatureSwitch to extensions/common/switches.h (when necessary).
Update some uses of the switches to use feature switch instead of the commandline

BUG=159265
TBR=rdsmith@chromium.org (c/b/download)
TBR=sky@chromium.org (c/b/ui/, c/test/ui/)

Review URL: https://codereview.chromium.org/47923018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233977 0039d316-1c4b-4281-b951-d872f2087c98
Increases tolerance for touch-snapping near the screen edges

BUG=316645
TEST=ash_unittests --gtest_filter=*SystemGestureEventFilterTest.Drag*NearEdgeSnaps*

Review URL: https://codereview.chromium.org/58973004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233978 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233977
SVN changes up to revision 233978