Inline traversal pooling logic into ReactChildren

scripts/rollup/packaging.js

@@ -24,7 +24,7 @@ const facebookWWWSrcDependencies = [
 
 // these files need to be copied to the react-native build
 const reactNativeSrcDependencies = [
-  'src/shared/utils/PooledClass.js',
+  'src/renderers/shared/utils/PooledClass.js',
   'src/renderers/shared/fiber/isomorphic/ReactTypes.js',
   'src/renderers/native/ReactNativeTypes.js',
 ];

scripts/rollup/results.json

@@ -1,28 +1,28 @@
 {
   "bundleSizes": {
     "react.development.js (UMD_DEV)": {
-      "size": 69376,
-      "gzip": 17780
+      "size": 65151,
+      "gzip": 16692
     },
     "react.production.min.js (UMD_PROD)": {
-      "size": 7585,
-      "gzip": 3002
+      "size": 6489,
+      "gzip": 2704
     },
     "react.development.js (NODE_DEV)": {
-      "size": 59667,
-      "gzip": 15411
+      "size": 55446,
+      "gzip": 14337
     },
     "react.production.min.js (NODE_PROD)": {
-      "size": 6451,
-      "gzip": 2576
+      "size": 5352,
+      "gzip": 2269
     },
     "React-dev.js (FB_DEV)": {
-      "size": 56905,
-      "gzip": 14622
+      "size": 52704,
+      "gzip": 13552
     },
     "React-prod.js (FB_PROD)": {
-      "size": 27099,
-      "gzip": 7215
+      "size": 24229,
+      "gzip": 6612
     },
     "react-dom.development.js (UMD_DEV)": {
       "size": 624799,

src/isomorphic/children/ReactChildren.js

@@ -11,15 +11,11 @@
 
 'use strict';
 
-var PooledClass = require('PooledClass');
 var ReactElement = require('ReactElement');
 
 var emptyFunction = require('fbjs/lib/emptyFunction');
 var invariant = require('fbjs/lib/invariant');
 
-var twoArgumentPooler = PooledClass.twoArgumentPooler;
-var fourArgumentPooler = PooledClass.fourArgumentPooler;
-
 if (__DEV__) {
   var warning = require('fbjs/lib/warning');
   var {getStackAddendum} = require('ReactDebugCurrentFrame');
@@ -244,40 +240,53 @@ function forEachChildren(children, forEachFunc, forEachContext) {
   if (children == null) {
     return children;
   }
-  var traverseContext = MapBookKeeping.getPooled(
+  var traverseContext = getPooledTraverseContext(
     null,
     null,
     forEachFunc,
     forEachContext,
   );
   traverseAllChildren(children, forEachSingleChild, traverseContext);
-  MapBookKeeping.release(traverseContext);
+  releaseTraverseContext(traverseContext);
 }
 
-/**
- * PooledClass representing the bookkeeping associated with performing a child
- * mapping. Allows avoiding binding callbacks.
- *
- * @constructor MapBookKeeping
- * @param {!*} mapResult Object containing the ordered map of results.
- * @param {!function} mapFunction Function to perform mapping with.
- * @param {?*} mapContext Context to perform mapping with.
- */
-function MapBookKeeping(mapResult, keyPrefix, mapFunction, mapContext) {
-  this.result = mapResult;
-  this.keyPrefix = keyPrefix;
-  this.func = mapFunction;
-  this.context = mapContext;
-  this.count = 0;
+var POOL_SIZE = 10;
+var traverseContextPool = [];
+function getPooledTraverseContext(
+  mapResult,
+  keyPrefix,
+  mapFunction,
+  mapContext,
+) {
+  if (traverseContextPool.length) {
+    var traverseContext = traverseContextPool.pop();
+    traverseContext.result = mapResult;
+    traverseContext.keyPrefix = keyPrefix;
+    traverseContext.func = mapFunction;
+    traverseContext.context = mapContext;
+    traverseContext.count = 0;
+    return traverseContext;
+  } else {
+    return {
+      result: mapResult,
+      keyPrefix: keyPrefix,
+      func: mapFunction,
+      context: mapContext,
+      count: 0,
+    };
+  }
+}
+
+function releaseTraverseContext(traverseContext) {
+  traverseContext.result = null;
+  traverseContext.keyPrefix = null;
+  traverseContext.func = null;
+  traverseContext.context = null;
+  traverseContext.count = 0;
+  if (traverseContextPool.length < POOL_SIZE) {
+    traverseContextPool.push(traverseContext);
+  }
 }
-MapBookKeeping.prototype.destructor = function() {
-  this.result = null;
-  this.keyPrefix = null;
-  this.func = null;
-  this.context = null;
-  this.count = 0;
-};
-PooledClass.addPoolingTo(MapBookKeeping, fourArgumentPooler);
 
 function mapSingleChildIntoContext(bookKeeping, child, childKey) {
   var {result, keyPrefix, func, context} = bookKeeping;
@@ -312,14 +321,14 @@ function mapIntoWithKeyPrefixInternal(children, array, prefix, func, context) {
   if (prefix != null) {
     escapedPrefix = escapeUserProvidedKey(prefix) + '/';
   }
-  var traverseContext = MapBookKeeping.getPooled(
+  var traverseContext = getPooledTraverseContext(
     array,
     escapedPrefix,
     func,
     context,
   );
   traverseAllChildren(children, mapSingleChildIntoContext, traverseContext);
-  MapBookKeeping.release(traverseContext);
+  releaseTraverseContext(traverseContext);
 }
 
 /**