Fix parenting of touch editing handles and quick menu

Previously, TouchEditableImplAura returned the root window as its native
view which was used as the parent of touch editing handles and quick
menu. This caused some positioning problems in external display. Here,
TouchEditableImplAura is changed to return the browser window as its
native view (similar to Views::Textfield's current behavior).

BUG=339627

Review URL: https://codereview.chromium.org/166443005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252099 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252099