Make SVGLength wrap a CSSPrimitiveValue.

third_party/WebKit/LayoutTests/svg/dom/script-tests/SVGLength.js

Index: third_party/WebKit/LayoutTests/svg/dom/script-tests/SVGLength.js
diff --git a/third_party/WebKit/LayoutTests/svg/dom/script-tests/SVGLength.js b/third_party/WebKit/LayoutTests/svg/dom/script-tests/SVGLength.js
index ba7663d12828bd6f62ef890bf10582828766aeb6..01d8279cd827a3920f0ba3409f0f0077cb5f6d5a 100644
--- a/third_party/WebKit/LayoutTests/svg/dom/script-tests/SVGLength.js
+++ b/third_party/WebKit/LayoutTests/svg/dom/script-tests/SVGLength.js
@@ -71,12 +71,14 @@ shouldBe("length.value", "2");
 shouldBe("length.valueInSpecifiedUnits", "2");
 shouldBe("length.unitType", "SVGLength.SVG_LENGTHTYPE_PX");
 
-shouldThrow("length.valueAsString = '1pX'");
-shouldBeEqualToString("length.valueAsString", "2px");
-shouldBe("length.value", "2");
-shouldBe("length.valueInSpecifiedUnits", "2");
+shouldNotThrow("length.valueAsString = '1pX'");
+shouldBeEqualToString("length.valueAsString", "1px");
+shouldBe("length.value", "1");
+shouldBe("length.valueInSpecifiedUnits", "1");
 shouldBe("length.unitType", "SVGLength.SVG_LENGTHTYPE_PX");
 
+length.valueAsString = "2px"; // reset to 2px
+
 shouldThrow("length.valueAsString = ',5 em'");
 shouldBeEqualToString("length.valueAsString", "2px");
 shouldBe("length.value", "2");