SVG Library cleanups and adding supported tag.

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 0fbdacb9d77ebdf7343d0f52ef694ec203cf8245..97656ba3751d0d4412aefb026aea62bdd2527109 100644
--- a/tools/dom/templates/html/impl/impl_SVGElement.darttemplate
+++ b/tools/dom/templates/html/impl/impl_SVGElement.darttemplate
@@ -111,5 +111,14 @@ $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
     throw new UnsupportedError("Cannot invoke click SVG.");
   }
 
+  /**
+   * Checks to see if the SVG element type is supported by the current platform.
+   *
+   * The tag should be a valid SVG element tag name.
+   */
+  static bool isTagSupported(String tag) {
+    var e = new $CLASSNAME.tag(tag);
+    return e is $CLASSNAME && !(e is UnknownElement);
+  }
 $!MEMBERS
 }