Changed definition of IntervalTree to contain closed, rather than
open, intervals, and changed back PathProcessor's
AllSegmentsOverlappingY debug routine to report closed intervals. This
fixes more rendering issues with the SVG butterfly.

BUG=none
TEST=samples/gpu2d/regression-tests/orientation-bug-3.html
TBR=apatrick

Review URL: http://codereview.chromium.org/2847049

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@51670 0039d316-1c4b-4281-b951-d872f2087c98