editing/selection/extend-selection.html times out in debug mode. mark it as slow.
editing/selection/extend-selection.html times out in debug mode.
mark it as slow.

TBR=arv
BUG=39855
TEST=none

Review URL: http://codereview.chromium.org/1518014

git-svn-id: http://src.chromium.org/svn/trunk/src@43490 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: dac1ed536bc8bbe3a14798b366b16d6de71ecafe
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser