Fix fiber feature flag for ReactDOMProduction-test

scripts/fiber/tests-failing.txt

@@ -24,6 +24,9 @@ src/renderers/art/__tests__/ReactART-test.js
 * resolves refs before componentDidMount
 * resolves refs before componentDidUpdate
 
+src/renderers/dom/__tests__/ReactDOMProduction-test.js
+* should throw with an error code in production
+
 src/renderers/dom/shared/__tests__/ReactDOM-test.js
 * throws in render() if the mount callback is not a function
 * throws in render() if the update callback is not a function

scripts/fiber/tests-passing.txt

@@ -488,7 +488,6 @@ src/renderers/dom/__tests__/ReactDOMProduction-test.js
 * should use prod React
 * should handle a simple flow
 * should call lifecycle methods
-* should throw with an error code in production
 
 src/renderers/dom/fiber/__tests__/ReactDOMFiber-test.js
 * should render strings as children

src/isomorphic/classic/types/__tests__/ReactPropTypesProduction-test.js

@@ -22,7 +22,9 @@ describe('ReactPropTypesProduction', function() {
   beforeEach(function() {
     __DEV__ = false;
     oldProcess = process;
-    global.process = {env: {NODE_ENV: 'production'}};
+    global.process = {
+      env: Object.assign({}, process.env, {NODE_ENV: 'production'}),
+    };
 
     jest.resetModuleRegistry();
     PropTypes = require('ReactPropTypes');

src/renderers/dom/__tests__/ReactDOMProduction-test.js

@@ -19,7 +19,9 @@ describe('ReactDOMProduction', () => {
   beforeEach(() => {
     __DEV__ = false;
     oldProcess = process;
-    global.process = {env: {NODE_ENV: 'production'}};
+    global.process = {
+      env: Object.assign({}, process.env, {NODE_ENV: 'production'}),
+    };
 
     jest.resetModuleRegistry();
     React = require('React');

src/renderers/shared/utils/__tests__/ReactErrorUtils-test.js

@@ -60,7 +60,9 @@ describe('ReactErrorUtils', () => {
       );
       __DEV__ = false;
       var oldProcess = process;
-      global.process = {env: {NODE_ENV: 'production'}};
+      global.process = {
+        env: Object.assign({}, process.env, {NODE_ENV: 'production'}),
+      };
       jest.resetModuleRegistry();
       ReactErrorUtils = require('ReactErrorUtils');
       expect(ReactErrorUtils.invokeGuardedCallback).toEqual(