Add NativeProfiling module that uses RN nativeProfiler or console.profile

Reviewed By: jspahrsummers

Differential Revision: D2696072

fb-gh-sync-id: 6a2b9793424cf9a82b9472e6d468cbd81dd6780a

Libraries/Utilities/CPUProfiler.js

@@ -0,0 +1,43 @@
+/**
+ * Copyright (c) 2015-present, 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 CPUProfiler
+ * @flow
+ */
+'use strict';
+
+var _label;
+var _nestingLevel = 0;
+
+var CPUProfiler = {
+
+  start(profileName: string) {
+    if (_nestingLevel === 0) {
+      if (global.nativeProfilerStart) {
+        _label = profileName;
+        global.nativeProfilerStart(profileName);
+      } else if (console.profile) {
+        console.profile(profileName);
+      }
+    }
+    _nestingLevel++;
+  },
+  end() {
+    _nestingLevel--;
+    if (_nestingLevel === 0) {
+      if (global.nativeProfilerEnd) {
+        global.nativeProfilerEnd(_label);
+      } else if (console.profileEnd) {
+        console.profileEnd();
+      }
+      _label = undefined;
+    }
+  }
+};
+
+module.exports = CPUProfiler;