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

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

 description('Test that setting and getting grid-definition-columns and grid-definition-rows works as expected');
 
 debug("Test getting grid-definition-columns and grid-definition-rows set through CSS");
 var gridWithNoneElement = document.getElementById("gridWithNoneElement");
 shouldBe("getComputedStyle(gridWithNoneElement, '').getPropertyValue('grid-definition-columns')", "'none'");
 shouldBe("getComputedStyle(gridWithNoneElement, '').getPropertyValue('grid-definition-rows')", "'none'");
 
 var gridWithFixedElement = document.getElementById("gridWithFixedElement");
 shouldBe("getComputedStyle(gridWithFixedElement, '').getPropertyValue('grid-definition-columns')", "'10px'");
 shouldBe("getComputedStyle(gridWithFixedElement, '').getPropertyValue('grid-definition-rows')", "'15px'");
@@ skipping 223 matching lines @@
 element.style.gridDefinitionColumns = ".0000fr";
 element.style.gridDefinitionRows = "13 fr"; // A dimension doesn't allow spaces between the number and the unit.
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
 
 element.style.gridDefinitionColumns = "7.-fr";
 element.style.gridDefinitionRows = "-8,0fr";
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
 
+// Negative values are not allowed.
+element.style.gridDefinitionColumns = "-1px";
+element.style.gridDefinitionRows = "-6em";
+shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
+shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
+
+element.style.gridDefinitionColumns = "minmax(-1%, 32%)";
+element.style.gridDefinitionRows = "minmax(2vw, -6em)";
+shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
+shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
+
 debug("");
 debug("Test setting grid-definition-columns and grid-definition-rows back to 'none' through JS");
 element.style.gridDefinitionColumns = "18px";
 element.style.gridDefinitionRows = "66px";
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'18px'");
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'66px'");
 element.style.gridDefinitionColumns = "none";
 element.style.gridDefinitionRows = "none";
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-columns')", "'none'");
 shouldBe("getComputedStyle(element, '').getPropertyValue('grid-definition-rows')", "'none'");
@@ skipping 30 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();