Fix identity and SVGAnimatedString issues with element_classes_test

tools/dom/templates/html/impl/impl_SVGElement.darttemplate

Index: tools/dom/templates/html/impl/impl_SVGElement.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_SVGElement.darttemplate b/tools/dom/templates/html/impl/impl_SVGElement.darttemplate
index 378dec8a2a3a4ea5c5ec4c86d0822b4a34e3e6ea..e417a464c81c41b52dbe8ecb7d62c1756bfa5aa3 100644
--- a/tools/dom/templates/html/impl/impl_SVGElement.darttemplate
+++ b/tools/dom/templates/html/impl/impl_SVGElement.darttemplate
@@ -143,5 +143,18 @@ $(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS
     var e = new $CLASSNAME.tag(tag);
     return e is $CLASSNAME && !(e is UnknownElement);
   }
+
+$if JSINTEROP
+  String get className => _svgClassName.baseVal;
+
+  // Unbelievable hack. We can't create an SvgAnimatedString, but we can get
+  // the existing one and change its baseVal.
+  // TODO(alanknight): Handle suppressing the SVGAnimated<*> better
+  set className(String s) {
+    var oldClass = _svgClassName;
+    oldClass.baseVal = s;
+    super.className = oldClass;
+  }
+$endif

[terry, 2015/08/17 14:40:29]

Is it a bug that we can't create an SvgAnimatedString?  There is a create method
but the IDL doesn't expose that should we be able to construct an
SvgAnimatedString by allowing a constructor to call create?

 $!MEMBERS
 }