CSSStyleDeclaraction returns empty string

LayoutTests/css3/calc/number-parsing.html

Index: LayoutTests/css3/calc/number-parsing.html
diff --git a/LayoutTests/css3/calc/number-parsing.html b/LayoutTests/css3/calc/number-parsing.html
index 021c75559f0424f14c3d4724dbccae5c0f06a5ce..44e8d70446b1c79f9ab749daf1868d440cfb2430 100644
--- a/LayoutTests/css3/calc/number-parsing.html
+++ b/LayoutTests/css3/calc/number-parsing.html
@@ -10,19 +10,19 @@ function assertParsedValue(property, input, expected) {
 
 test(function() {
   assertParsedValue('-webkit-box-ordinal-group', 'calc(6 + 4)', '10');
-  assertParsedValue('-webkit-box-ordinal-group', 'calc(0)', null);
-  assertParsedValue('-webkit-column-span', 'calc(2 - 1)', null);
-  assertParsedValue('-webkit-column-span', 'calc(1 + 2)', null);
+  assertParsedValue('-webkit-box-ordinal-group', 'calc(0)', '');
+  assertParsedValue('-webkit-column-span', 'calc(2 - 1)', '');
+  assertParsedValue('-webkit-column-span', 'calc(1 + 2)', '');
   assertParsedValue('-webkit-column-width', 'calc(1em - 1px)', 'calc(1em - 1px)');
-  assertParsedValue('transition-timing-function', 'cubic-bezier(calc(1 + 2), 0, 1, 1)', null);
+  assertParsedValue('transition-timing-function', 'cubic-bezier(calc(1 + 2), 0, 1, 1)', '');
   assertParsedValue('transition-timing-function', 'cubic-bezier(calc(1 / 2), calc(1 - 1), calc(2 - 1), calc(2 * 3))', 'cubic-bezier(0.5, 0, 1, 6)');
   assertParsedValue('transition-timing-function', 'steps(calc(1 + 2), start)', 'steps(3, start)');
   assertParsedValue('grid-row-start', 'calc(1 + 2) test', '3 test');
-  assertParsedValue('grid-row-start', 'calc(1 / 2) test', null);
-  assertParsedValue('font-weight', 'calc(100 + 200)', null);
+  assertParsedValue('grid-row-start', 'calc(1 / 2) test', '');
+  assertParsedValue('font-weight', 'calc(100 + 200)', '');
   assertParsedValue('flex', 'calc(1 + 2) calc(3 + 4)', '3 7 0%');
   assertParsedValue('-webkit-filter', 'saturate(calc(4 / 2))', 'saturate(2)');
-  assertParsedValue('-webkit-filter', 'invert(calc(4 / 2))', null);
+  assertParsedValue('-webkit-filter', 'invert(calc(4 / 2))', '');
   assertParsedValue('-webkit-filter', 'invert(calc(2 / 4))', 'invert(0.5)');
   assertParsedValue('-webkit-filter', 'brightness(calc(4 / 2))', 'brightness(2)');
 }, 'Ensure using calc() for CSS numbers does not crash or produce incorrect values.');