[Fiber] fix ensure class components refs get re-assigned to emptyObject on mount

scripts/fiber/tests-failing.txt

@@ -19,9 +19,6 @@ src/renderers/__tests__/ReactPerf-test.js
 * should not count time in a portal towards lifecycle method
 * should work when measurement starts during reconciliation
 
-src/renderers/__tests__/refs-test.js
-* Should increase refs with an increase in divs
-
 src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js
 * gives source code refs for unknown prop warning (ssr)
 * gives source code refs for unknown prop warning for exact elements (ssr)

scripts/fiber/tests-passing.txt

@@ -841,6 +841,8 @@ src/renderers/__tests__/refs-destruction-test.js
 * should not error when destroying child with ref asynchronously
 
 src/renderers/__tests__/refs-test.js
+* Should increase refs with an increase in divs
+* Should correctly get the ref
 * Allow refs to hop around children correctly
 * always has a value for this.refs
 * ref called correctly for stateless component when __DEV__ = false

src/renderers/__tests__/refs-test.js

@@ -144,12 +144,23 @@ describe('reactiverefs', () => {
     // Now reset again
     ReactTestUtils.Simulate.click(testRefsComponent.refs.resetDiv);
     expectClickLogsLengthToBe(testRefsComponent, 1);
-
   });
-
 });
 
+describe('factory components', () => {
+  it('Should correctly get the ref', () => {
+    function Comp() {
+      return {
+        render() {
+          return <div ref="elemRef" />;
+        },
+      };
+    }
 
+    const inst = ReactTestUtils.renderIntoDocument(<Comp />);
+    expect(inst.refs.elemRef.tagName).toBe('DIV');
+  });
+});
 
 /**
  * Tests that when a ref hops around children, we can track that correctly.

src/renderers/shared/fiber/ReactFiberClassComponent.js

@@ -291,6 +291,7 @@ module.exports = function(
 
     instance.props = props;
     instance.state = state;
+    instance.refs = emptyObject;
     instance.context = getMaskedContext(workInProgress, unmaskedContext);
 
     if (typeof instance.componentWillMount === 'function') {