Update expected cssText for custom property serialization

See https://github.com/w3c/csswg-drafts/issues/2509#issuecomment-379152590 for the change to target9. Also remove the extra whitespace in target8 and target1 which causes these tests to fail in Chrome and Firefox.

Also remove testcase.propertyName from each test's name as this doesn't exist and just outputs undefined.
diff --git a/css/css-variables/variable-cssText.html b/css/css-variables/variable-cssText.html
index fd70ce9..b61d297 100644
--- a/css/css-variables/variable-cssText.html
+++ b/css/css-variables/variable-cssText.html
@@ -28,15 +28,15 @@
     "use strict";
 
     var testcases = [
-        { element: "target1",   expectedCssText: "--var:  var1;" },
+        { element: "target1",   expectedCssText: "--var: var1;" },
         { element: "target2",   expectedCssText: "margin: var(--prop);" },
         { element: "target3",   expectedCssText: "background: var(--prop);" },
         { element: "target4",   expectedCssText: "margin: var(--prop)  !important;" },
         { element: "target5",   expectedCssText: "background: var(--prop)  !important;" },
         { element: "target6",   expectedCssText: "background: green;" },
         { element: "target7",   expectedCssText: "background: var(--prop);" },
-        { element: "target8",   expectedCssText: "color:  var(--prop);" },
-        { element: "target9",   expectedCssText: "margin-top: 10px; margin-right: ; margin-bottom: ; margin-left: ;" },
+        { element: "target8",   expectedCssText: "color: var(--prop);" },
+        { element: "target9",   expectedCssText: "margin-right: ; margin-bottom: ; margin-left: ; margin-top: 10px;" },
         { element: "target10",  expectedCssText: "" }
     ];
 
@@ -45,7 +45,7 @@
             var div = document.getElementById(testcase.element);
             var actualCssText = div.style.cssText;
             assert_equals(actualCssText, testcase.expectedCssText);
-        }, testcase.element + " " + testcase.propertyName);
+        }, testcase.element);
     });
 </script>