More fixes for issues introduced by rebasing

**what is the change?:**
- Remove some outdated 'require' statements that got orphaned in 'React.js'
- Change 'warning' to 'lowPriorityWarning' for 'React.createClass'
- Fix syntax issues in 'React-test'
- Use 'creatReactClass' instead of ES6 class in ReactART

**why make this change?:**
These were bugs introduced by rebasing and tests caught the regressions.

**test plan:**
`yarn test`

**issue:**
#9398

Author: flarnie

src/isomorphic/React.js

@@ -13,16 +13,13 @@
 
 var ReactBaseClasses = require('ReactBaseClasses');
 var ReactChildren = require('ReactChildren');
-var ReactComponent = require('ReactComponent');
-var ReactPureComponent = require('ReactPureComponent');
 var ReactDOMFactories = require('ReactDOMFactories');
 var ReactElement = require('ReactElement');
 var ReactPropTypes = require('ReactPropTypes');
 var ReactVersion = require('ReactVersion');
 
 var createReactClass = require('createClass');
 var onlyChild = require('onlyChild');
-var warning = require('warning');
 
 var createElement = ReactElement.createElement;
 var createFactory = ReactElement.createFactory;
@@ -112,7 +109,7 @@ if (__DEV__) {
 
     Object.defineProperty(React, 'createClass', {
       get: function() {
-        warning(
+        lowPriorityWarning(
           warnedForCreateClass,
           'React.createClass is no longer supported. Use a plain JavaScript ' +
             "class instead. If you're not yet ready to migrate, " +

src/isomorphic/__tests__/React-test.js

@@ -39,12 +39,12 @@ describe('React', () => {
   });
 
   it('should warn once when attempting to access React.createClass', () => {
-    spyOn(console, 'error');
+    spyOn(console, 'warn');
     let createClass = React.createClass;
     createClass = React.createClass;
     expect(createClass).not.toBe(undefined);
-    expectDev(console.error.calls.count()).toBe(1);
-    expectDev(console.error.calls.argsFor(0)[0]).toContain(
+    expect(console.warn.calls.count()).toBe(1);
+    expect(console.warn.calls.argsFor(0)[0]).toContain(
       'React.createClass is no longer supported. Use a plain ' +
         "JavaScript class instead. If you're not yet ready to migrate, " +
         'create-react-class is available on npm as a temporary, ' +
@@ -53,12 +53,12 @@ describe('React', () => {
   });
 
   it('should warn once when attempting to access React.PropTypes', () => {
-    spyOn(console, 'error');
+    spyOn(console, 'warn');
     let PropTypes = React.PropTypes;
     PropTypes = React.PropTypes;
     expect(PropTypes).not.toBe(undefined);
-    expectDev(console.error.calls.count()).toBe(1);
-    expectDev(console.error.calls.argsFor(0)[0]).toContain(
+    expect(console.warn.calls.count()).toBe(1);
+    expect(console.warn.calls.argsFor(0)[0]).toContain(
       'PropTypes have moved out of the react package. ' +
         'Use the prop-types package from npm instead.',
     );

src/renderers/art/ReactART.js

@@ -24,6 +24,7 @@ const ReactInstanceMap = require('ReactInstanceMap');
 const ReactMultiChild = require('ReactMultiChild');
 const ReactUpdates = require('ReactUpdates');
 
+const createReactClass = require('createClass');
 const emptyObject = require('emptyObject');
 const invariant = require('invariant');
 
@@ -171,8 +172,12 @@ const ContainerMixin = assign({}, ReactMultiChild.Mixin, {
 // Surface is a React DOM Component, not an ART component. It serves as the
 // entry point into the ART reconciler.
 
-class Surface extends React.Component {
-  componentDidMount() {
+const Surface = createReactClass({
+  displayName: 'Surface',
+
+  mixins: [ContainerMixin],
+
+  componentDidMount: function() {
     const domNode = ReactDOM.findDOMNode(this);
 
     this.node = Mode.Surface(+this.props.width, +this.props.height, domNode);
@@ -186,9 +191,9 @@ class Surface extends React.Component {
       ReactInstanceMap.get(this)._context,
     );
     ReactUpdates.ReactReconcileTransaction.release(transaction);
-  }
+  },
 
-  componentDidUpdate(oldProps) {
+  componentDidUpdate: function(oldProps) {
     const node = this.node;
     if (
       this.props.width != oldProps.width ||
@@ -210,13 +215,13 @@ class Surface extends React.Component {
     if (node.render) {
       node.render();
     }
-  }
+  },
 
-  componentWillUnmount() {
+  componentWillUnmount: function() {
     this.unmountChildren();
-  }
+  },
 
-  render() {
+  render: function() {
     // This is going to be a placeholder because we don't know what it will
     // actually resolve to because ART may render canvas, vml or svg tags here.
     // We only allow a subset of properties since others might conflict with
@@ -234,8 +239,8 @@ class Surface extends React.Component {
         title={props.title}
       />
     );
-  }
-}
+  },
+});
 
 // Various nodes that can go into a surface