input[type=range]: Updating step attribute should align the value to steps.

third_party/WebKit/LayoutTests/fast/forms/range/ValidityState-stepMismatch-range.html

Index: third_party/WebKit/LayoutTests/fast/forms/range/ValidityState-stepMismatch-range.html
diff --git a/third_party/WebKit/LayoutTests/fast/forms/range/ValidityState-stepMismatch-range.html b/third_party/WebKit/LayoutTests/fast/forms/range/ValidityState-stepMismatch-range.html
index 8b3b38503b17a5fc983269484f1a519b3d988d40..82aa78c0c8b6a6ca9b28a6cabd8c32890c663ee0 100644
--- a/third_party/WebKit/LayoutTests/fast/forms/range/ValidityState-stepMismatch-range.html
+++ b/third_party/WebKit/LayoutTests/fast/forms/range/ValidityState-stepMismatch-range.html
@@ -35,6 +35,16 @@ input.max = '';
 shouldBe('stepMismatchFor("-3", "-2", "-4")', 'false');
 shouldBe('stepMismatchFor("-3", null, "-4")', 'false');
 shouldBe('stepMismatchFor("-3", undefined, "-4")', 'false');
+
+debug('Updating step attribute');
+stepMismatchFor('50', '10', '0');
+shouldBeEqualToString('input.value', '50');
+shouldBeEqualToString('input.step = "15"; input.value', '45');
+shouldBeEqualToString('input.step = "20"; input.value', '40');
+stepMismatchFor('50', '10', '0');
+shouldBeEqualToString('input.value = "5", input.value', '10');
+shouldBeEqualToString('input.step = "6"; input.value', '12');
+
 debug('Huge numbers and small step; uncomparable');
 shouldBe('stepMismatchFor("3.40282347e+38", "3", "")', 'false');
 shouldBe('stepMismatchFor("3.40282346e+38", "3", "")', 'false');