[CSS Grid Layout] infinity should be defined as a negative value

LayoutTests/fast/css-grid-layout/resources/grid-columns-rows-get-set-multiple.js

 description('Test that setting and getting grid-definition-columns and grid-definition-rows works as expected');
 
 debug("Test getting |display| set through CSS");
 var gridWithFixedElement = document.getElementById("gridWithFixedElement");
 shouldBe("getComputedStyle(gridWithFixedElement, '').getPropertyValue('grid-definition-columns')", "'7px 11px'");
 shouldBe("getComputedStyle(gridWithFixedElement, '').getPropertyValue('grid-definition-rows')", "'17px 2px'");
 
 var gridWithPercentElement = document.getElementById("gridWithPercentElement");
 shouldBe("getComputedStyle(gridWithPercentElement, '').getPropertyValue('grid-definition-columns')", "'53% 99%'");
 shouldBe("getComputedStyle(gridWithPercentElement, '').getPropertyValue('grid-definition-rows')", "'27% 52%'");
@@ skipping 151 matching lines @@
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
 
 element = document.createElement("div");
 document.body.appendChild(element);
 element.style.gridDefinitionColumns = "auto minmax(16px, auto)";
 element.style.gridDefinitionRows = "minmax(auto, 15%) 10vw";
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
 
+// Negative values are not allowed.
+element = document.createElement("div");
+document.body.appendChild(element);
+element.style.gridDefinitionColumns = "-10px minmax(16px, 32px)";
+element.style.gridDefinitionRows = "minmax(10%, 15%) -10vw";
+shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
+shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
+
+element = document.createElement("div");
+document.body.appendChild(element);
+element.style.gridDefinitionColumns = "10px minmax(16px, -1vw)";
+element.style.gridDefinitionRows = "minmax(-1%, 15%) 10vw";
+shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
+shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
+
 function testInherit()
 {
     var parentElement = document.createElement("div");
     document.body.appendChild(parentElement);
     parentElement.style.gridDefinitionColumns = "50px 1fr 'last'";
     parentElement.style.gridDefinitionRows = "101% 'middle' 45px";
 
     element = document.createElement("div");
     parentElement.appendChild(element);
     element.style.gridDefinitionColumns = "inherit";
@@ skipping 19 matching lines @@
     element.style.gridDefinitionColumns = "initial";
     element.style.gridDefinitionRows = "initial";
     shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
     shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
 
     document.body.removeChild(element);
 }
 debug("");
 debug("Test setting grid-definition-columns and grid-definition-rows to 'initial' through JS");
 testInitial();