Entering anything that's not a non-negative number turns the text field value into NaN and puts NaN into the property declaration in the sidebar. In this case, I would expect it to not edit the property declaration in the rule. It should highlight the bad value in red and explain why it's invalid (perhaps with a popover when hovered/selected), allowing the user to fix it themselves or click a button to revert.
<rdar://problem/29971394>
Created attachment 298602 [details] Patch
(In reply to comment #0) > It should highlight the bad value in red and explain why it's invalid > (perhaps with a popover when hovered/selected), allowing the user to fix it > themselves or click a button to revert. I think that adding this really would be a bit too much clutter (popovers inside popovers). I think that just having the input show a number "stepper" (not sure what to call the up/down arrow for <input type="number"> elements) implies that the value should be a number.
Comment on attachment 298602 [details] Patch Attachment 298602 [details] did not pass mac-wk2-ews (mac-wk2): Output: http://webkit-queues.webkit.org/results/2874902 Number of test failures exceeded the failure limit.
Created attachment 298655 [details] Archive of layout-test-results from ews105 for mac-elcapitan-wk2 The attached test failures were seen while running run-webkit-tests on the mac-wk2-ews. Bot: ews105 Port: mac-elcapitan-wk2 Platform: Mac OS X 10.11.6
Created attachment 298658 [details] Patch
Comment on attachment 298658 [details] Patch r=me
Comment on attachment 298658 [details] Patch Clearing flags on attachment: 298658 Committed r210674: <http://trac.webkit.org/changeset/210674>
All reviewed patches have been landed. Closing bug.