[CSS Grid Layout] Small refactoring in grid-auto-flow-get-set.html test

LayoutTests/fast/css-grid-layout/resources/grid-definitions-parsing-utils.js

 function testGridDefinitionsValues(element, columnValue, rowValue, computedColumnValue, computedRowValue)
 {
     window.element = element;
     var elementID = element.id || "element";
     shouldBeEqualToString("window.getComputedStyle(" + elementID + ", '').getPropertyValue('grid-template-columns')", computedColumnValue || columnValue);
     shouldBeEqualToString("window.getComputedStyle(" + elementID + ", '').getPropertyValue('grid-template-rows')", computedRowValue || rowValue);
 }
 
 function testGridDefinitionsSetJSValues(columnValue, rowValue, computedColumnValue, computedRowValue, jsColumnValue, jsRowValue)
 {
@@ skipping 26 matching lines @@
 
 function testGridDefinitionsSetBadJSValues(columnValue, rowValue)
 {
     window.element = document.createElement("div");
     document.body.appendChild(element);
     element.style.gridTemplateColumns = columnValue;
     element.style.gridTemplateRows = rowValue;
     // We can't use testSetJSValues as element.style.gridTemplateRows returns "".
     testGridDefinitionsValues(element, "none", "none");
     document.body.removeChild(element);
-}
+}
+
+function checkGridAutoFlowSetCSSValue(elementId, expectedValue)
+{
+    shouldBe("window.getComputedStyle(" + elementId + ", '').getPropertyValue('grid-auto-flow')", "'" + expectedValue + "'");
+}
+
+function checkGridAutoFlowSetJSValue(newValue, expectedStyleValue, expectedComputedStyleValue)
+{
+    element = document.createElement("div");
+    document.body.appendChild(element);
+    if (newValue)
+        element.style.gridAutoFlow = newValue;
+    shouldBe("element.style.gridAutoFlow", "'" + expectedStyleValue + "'");
+    shouldBe("window.getComputedStyle(element, '').getPropertyValue('grid-auto-flow')", "'" + expectedComputedStyleValue + "'");
+    document.body.removeChild(element);
+}