[perf] Change how ReactDefaultPerf is injected

ReactDefaultPerf should inject itself when require()'d. This continues to support the ?react_perf use case for logging on initial page load.

src/browser/ReactDefaultInjection.js

@@ -91,10 +91,6 @@ function inject() {
 
   ReactInjection.DOMProperty.injectDOMPropertyConfig(DefaultDOMPropertyConfig);
 
-  if (__DEV__) {
-    ReactInjection.Perf.injectMeasure(require('ReactDefaultPerf').measure);
-  }
-
   ReactInjection.Updates.injectBatchingStrategy(
     ReactDefaultBatchingStrategy
   );
@@ -104,6 +100,14 @@ function inject() {
       ClientReactRootIndex.createReactRootIndex :
       ServerReactRootIndex.createReactRootIndex
   );
+
+  if (__DEV__) {
+    var url = (ExecutionEnvironment.canUseDOM && window.location.href) || '';
+    if ((/[?&]react_perf\b/).test(url)) {
+      var ReactDefaultPerf = require('ReactDefaultPerf');
+      ReactDefaultPerf.start();
+    }
+  }
 }
 
 module.exports = {

src/test/ReactDefaultPerf.js

@@ -19,12 +19,27 @@
 
 "use strict";
 
+var ReactPerf = require('ReactPerf');
+
 var performanceNow = require('performanceNow');
 
 var ReactDefaultPerf = {};
 
 if (__DEV__) {
   ReactDefaultPerf = {
+    _injected: false,
+
+    start: function() {
+      if (!ReactDefaultPerf._injected) {
+        ReactPerf.injection.injectMeasure(ReactDefaultPerf.measure);
+      }
+      ReactPerf.enableMeasure = true;
+    },
+
+    stop: function() {
+      ReactPerf.enableMeasure = false;
+    },
+
     /**
      * Gets the stored information for a given object's function.
      *
@@ -293,7 +308,7 @@ if (__DEV__) {
     var STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg;
     var fnStr = fn.toString().replace(STRIP_COMMENTS, '');
     fnStr = fnStr.slice(fnStr.indexOf('(') + 1, fnStr.indexOf(')'));
-    return fnStr.match(/([^\s,]+)/g);
+    return fnStr.match(/([^\s,]+)/g) || [];
   };
 
   /**

src/test/ReactPerf.js

@@ -19,6 +19,10 @@
 
 "use strict";
 
+/**
+ * ReactPerf is a general AOP system designed to measure performance. This
+ * module only has the hooks: see ReactDefaultPerf for the analysis tool.
+ */
 var ReactPerf = {
   /**
    * Boolean to enable/disable measurement. Set to false by default to prevent
@@ -33,7 +37,7 @@ var ReactPerf = {
   storedMeasure: _noMeasure,
 
   /**
-   * Use this to wrap methods you want to measure.
+   * Use this to wrap methods you want to measure. Zero overhead in production.
    *
    * @param {string} objName
    * @param {string} fnName
@@ -66,13 +70,6 @@ var ReactPerf = {
   }
 };
 
-if (__DEV__) {
-  var ExecutionEnvironment = require('ExecutionEnvironment');
-  var url = (ExecutionEnvironment.canUseDOM && window.location.href) || '';
-  ReactPerf.enableMeasure = ReactPerf.enableMeasure ||
-    (/[?&]react_perf\b/).test(url);
-}
-
 /**
  * Simply passes through the measured function, without measuring it.
  *