WIP Downgrade deprecation warnings from errors to warnings

**RFC:**
Pushing this for feedback while I fix all the failing tests.

**what is the change?:**
Swapping out `warning` module for a fork that uses `console.warn`.
It looks like we were using the `warning` module for deprecation notices, *but* there is also a 'deprecated' module designed specifically for deprecation notices.

However, we could not find any place that it was currently used.

Since React's build process is not 100% clear to me, I assume it could still be used somewhere by something and just updated it along with other deprecation notices.

We might consider a follow-up diff that does some clean up here;
 - remove 'deprecated' module if it's unused, OR
 - use 'deprecated' module for all our current deprecation warnings

**why make this change?:**
- We have had complaints about noisy warnings, in particular after introducing new deprecations
- They potentially cause CI failures
- Deprecations are not really time-sensitive, can ship without breaking your app, etc.

For more context - facebook#9395

**test plan:**
`npm run test`
and unit tests for the new modules
and manual testing (WIP)

**issue:**
facebook#9395

src/isomorphic/React.js

@@ -27,7 +27,7 @@ var createFactory = ReactElement.createFactory;
 var cloneElement = ReactElement.cloneElement;
 
 if (__DEV__) {
-  var warning = require('fbjs/lib/warning');
+  var lowPriorityWarning = require('lowPriorityWarning');
   var canDefineProperty = require('canDefineProperty');
   var ReactElementValidator = require('ReactElementValidator');
   createElement = ReactElementValidator.createElement;
@@ -91,7 +91,7 @@ if (__DEV__) {
   let warnedForPropTypes = false;
 
   React.createMixin = function(mixin) {
-    warning(
+    lowPriorityWarning(
       warnedForCreateMixin,
       'React.createMixin is deprecated and should not be used. You ' +
         'can use this mixin directly instead.',
@@ -104,7 +104,7 @@ if (__DEV__) {
   if (canDefineProperty) {
     Object.defineProperty(React, 'checkPropTypes', {
       get() {
-        warning(
+        lowPriorityWarning(
           warnedForCheckPropTypes,
           'checkPropTypes has been moved to a separate package. ' +
             'Accessing React.checkPropTypes is no longer supported ' +
@@ -119,7 +119,7 @@ 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, " +
@@ -133,7 +133,7 @@ if (__DEV__) {
 
     Object.defineProperty(React, 'PropTypes', {
       get() {
-        warning(
+        lowPriorityWarning(
           warnedForPropTypes,
           'PropTypes has been moved to a separate package. ' +
             'Accessing React.PropTypes is no longer supported ' +
@@ -155,7 +155,7 @@ if (__DEV__) {
   Object.keys(ReactDOMFactories).forEach(function(factory) {
     React.DOM[factory] = function(...args) {
       if (!warnedForFactories) {
-        warning(
+        lowPriorityWarning(
           false,
           'Accessing factories like React.DOM.%s has been deprecated ' +
             'and will be removed in the future. Use the ' +

src/isomorphic/classic/element/ReactElementValidator.js

@@ -27,7 +27,7 @@ var getIteratorFn = require('getIteratorFn');
 
 if (__DEV__) {
   var checkPropTypes = require('prop-types/checkPropTypes');
-  var warning = require('fbjs/lib/warning');
+  var lowPriorityWarning = require('lowPriorityWarning');
   var ReactDebugCurrentFrame = require('ReactDebugCurrentFrame');
   var {getCurrentStackAddendum} = require('ReactComponentTreeHook');
 }
@@ -285,7 +285,7 @@ var ReactElementValidator = {
         Object.defineProperty(validatedFactory, 'type', {
           enumerable: false,
           get: function() {
-            warning(
+            lowPriorityWarning(
               false,
               'Factory.type is deprecated. Access the class directly ' +
                 'before passing it to createFactory.',

src/isomorphic/modern/class/ReactBaseClasses.js

@@ -16,7 +16,7 @@ var ReactNoopUpdateQueue = require('ReactNoopUpdateQueue');
 var canDefineProperty = require('canDefineProperty');
 var emptyObject = require('fbjs/lib/emptyObject');
 var invariant = require('fbjs/lib/invariant');
-var warning = require('fbjs/lib/warning');
+var lowPriorityWarning = require('lowPriorityWarning');
 
 /**
  * Base class helpers for the updating state of a component.
@@ -108,7 +108,7 @@ if (__DEV__) {
     if (canDefineProperty) {
       Object.defineProperty(ReactComponent.prototype, methodName, {
         get: function() {
-          warning(
+          lowPriorityWarning(
             false,
             '%s(...) is deprecated in plain JavaScript React classes. %s',
             info[0],

src/renderers/shared/ReactPerf.js

@@ -13,7 +13,7 @@
 'use strict';
 
 var ReactDebugTool = require('ReactDebugTool');
-var warning = require('fbjs/lib/warning');
+var lowPriorityWarning = require('lowPriorityWarning');
 var alreadyWarned = false;
 
 import type {FlushHistory} from 'ReactDebugTool';
@@ -390,7 +390,7 @@ function printOperations(flushHistory?: FlushHistory) {
 
 var warnedAboutPrintDOM = false;
 function printDOM(measurements: FlushHistory) {
-  warning(
+  lowPriorityWarning(
     warnedAboutPrintDOM,
     '`ReactPerf.printDOM(...)` is deprecated. Use ' +
       '`ReactPerf.printOperations(...)` instead.',
@@ -401,7 +401,7 @@ function printDOM(measurements: FlushHistory) {
 
 var warnedAboutGetMeasurementsSummaryMap = false;
 function getMeasurementsSummaryMap(measurements: FlushHistory) {
-  warning(
+  lowPriorityWarning(
     warnedAboutGetMeasurementsSummaryMap,
     '`ReactPerf.getMeasurementsSummaryMap(...)` is deprecated. Use ' +
       '`ReactPerf.getWasted(...)` instead.',

src/renderers/shared/fiber/ReactFiberClassComponent.js

@@ -45,6 +45,7 @@ const isArray = Array.isArray;
 if (__DEV__) {
   var {startPhaseTimer, stopPhaseTimer} = require('ReactDebugFiberPerf');
   var warning = require('fbjs/lib/warning');
+  var lowPriorityWarning = requier('lowPriorityWarning');
   var warnOnInvalidCallback = function(callback: mixed, callerName: string) {
     warning(
       callback === null || typeof callback === 'function',
@@ -316,7 +317,7 @@ module.exports = function(
 
     if (oldState !== instance.state) {
       if (__DEV__) {
-        warning(
+        lowPriorityWarning(
           false,
           '%s.componentWillMount(): Assigning directly to this.state is ' +
             "deprecated (except inside a component's " +
@@ -345,7 +346,7 @@ module.exports = function(
 
     if (instance.state !== oldState) {
       if (__DEV__) {
-        warning(
+        lowPriorityWarning(
           false,
           '%s.componentWillReceiveProps(): Assigning directly to ' +
             "this.state is deprecated (except inside a component's " +

src/renderers/shared/stack/reconciler/ReactCompositeComponent.js

@@ -30,6 +30,7 @@ if (__DEV__) {
 var checkPropTypes = require('prop-types/checkPropTypes');
 var emptyObject = require('fbjs/lib/emptyObject');
 var invariant = require('fbjs/lib/invariant');
+var lowPriorityWarning = require('lowPriorityWarning');
 var shallowEqual = require('fbjs/lib/shallowEqual');
 var shouldUpdateReactComponent = require('shouldUpdateReactComponent');
 var warning = require('fbjs/lib/warning');
@@ -879,7 +880,7 @@ var ReactCompositeComponent = {
         inst.state = beforeState;
         inst.updater.enqueueReplaceState(inst, afterState);
         if (__DEV__) {
-          warning(
+          lowPriorityWarning(
             false,
             '%s.componentWillReceiveProps(): Assigning directly to ' +
               "this.state is deprecated (except inside a component's " +

src/shared/utils/deprecated.js

@@ -12,7 +12,7 @@
 
 'use strict';
 
-var warning = require('fbjs/lib/warning');
+var lowPriorityWarning = require('lowPriorityWarning');
 
 /**
  * This will log a single deprecation notice per function and forward the call
@@ -35,7 +35,7 @@ function deprecated<T: Function>(
   var warned = false;
   if (__DEV__) {
     var newFn = function() {
-      warning(
+      lowPriorityWarning(
         warned,
         /* eslint-disable no-useless-concat */
         // Require examples in this string must be split to prevent React's

src/shared/utils/lowPriorityWarning.js

@@ -0,0 +1,41 @@
+/**
+ * Copyright 2014-2015, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule lowPriorityWarning
+ */
+
+'use strict';
+
+/**
+ * Forked from fbjs/warning:
+ * https://github.com/facebook/fbjs/blob/e66ba20ad5be433eb54423f2b097d829324d9de6/packages/fbjs/src/__forks__/warning.js
+ *
+ * Only change is we use console.warn instead of console.error,
+ * and do nothing when 'console' is not supported.
+ * This really simplifies the code.
+ * ---
+ *
+ * Similar to invariant but only logs a warning if the condition is not met.
+ * This can be used to log issues in development environments in critical
+ * paths. Removing the logging code for production environments will keep the
+ * same logic and follow the same code paths.
+ */
+
+var lowPriorityWarning = function() {};
+
+if (__DEV__) {
+  lowPriorityWarning = function(condition, format, ...args) {
+    var argIndex = 0;
+    var message = 'Warning: ' + format.replace(/%s/g, () => args[argIndex++]);
+    if (typeof console !== 'undefined') {
+      console.warn(message);
+    }
+  };
+}
+
+module.exports = lowPriorityWarning;