Handle className properly on SVG nodes

This strategy avoids a runtime check for every set (as opposed to using a mutation method).

Test Plan: Verify that changing className works on a div and a rect in latest Chrome, latest Firefox, IE9. Verify that the div works in IE8.

src/browser/ui/dom/HTMLDOMPropertyConfig.js

@@ -21,6 +21,7 @@
 "use strict";
 
 var DOMProperty = require('DOMProperty');
+var ExecutionEnvironment = require('ExecutionEnvironment');
 
 var MUST_USE_ATTRIBUTE = DOMProperty.injection.MUST_USE_ATTRIBUTE;
 var MUST_USE_PROPERTY = DOMProperty.injection.MUST_USE_PROPERTY;
@@ -32,6 +33,20 @@ var HAS_POSITIVE_NUMERIC_VALUE =
 var HAS_OVERLOADED_BOOLEAN_VALUE =
   DOMProperty.injection.HAS_OVERLOADED_BOOLEAN_VALUE;
 
+var hasSVG;
+if (ExecutionEnvironment.canUseDOM) {
+  var implementation = document.implementation;
+  hasSVG = (
+    implementation &&
+    implementation.hasFeature &&
+    implementation.hasFeature(
+      'http://www.w3.org/TR/SVG11/feature#BasicStructure',
+      '1.1'
+    )
+  );
+}
+
+
 var HTMLDOMPropertyConfig = {
   isCustomAttribute: RegExp.prototype.test.bind(
     /^(data|aria)-[a-z_][a-z\d_.\-]*$/
@@ -55,7 +70,12 @@ var HTMLDOMPropertyConfig = {
     cellSpacing: null,
     charSet: MUST_USE_ATTRIBUTE,
     checked: MUST_USE_PROPERTY | HAS_BOOLEAN_VALUE,
-    className: MUST_USE_PROPERTY,
+    // To set className on SVG elements, it's necessary to use .setAttribute;
+    // this works on HTML elements too in all browsers except IE8. Conveniently,
+    // IE8 doesn't support SVG and so we can simply use the attribute in
+    // browsers that support SVG and the property in browsers that don't,
+    // regardless of whether the element is HTML or SVG.
+    className: hasSVG ? MUST_USE_ATTRIBUTE : MUST_USE_PROPERTY,
     cols: MUST_USE_ATTRIBUTE | HAS_POSITIVE_NUMERIC_VALUE,
     colSpan: null,
     content: null,