Enable copying long text to Chrome and pasting long text from Chrome

      This CL adds support for the INCR property
(http://tronche.com/gui/x/icccm/sec-2.html#s-2.7.2) to SelectionRequestor and
SelectionOwner

BUG=367549
TEST=Manual, see bug
R=derat,dcheng,erg
TBR=erg for ui/base/BUILD.gn

Review URL: https://codereview.chromium.org/397223002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287404 0039d316-1c4b-4281-b951-d872f2087c98