Rename StatisticsBox to RenderStatisticsBox

Fixes #441

packages/flutter/lib/src/rendering/statistics_box.dart

@@ -5,9 +5,9 @@
 import 'box.dart';
 import 'object.dart';
 
-class StatisticsBox extends RenderBox {
+class RenderStatisticsBox extends RenderBox {
 
-  StatisticsBox({int optionsMask: 0, int rasterizerThreshold: 0})
+  RenderStatisticsBox({int optionsMask: 0, int rasterizerThreshold: 0})
     : _optionsMask = optionsMask,
       _rasterizerThreshold = rasterizerThreshold;
 

packages/flutter/lib/src/widgets/statistics_overlay.dart

@@ -83,12 +83,12 @@ class StatisticsOverlay extends LeafRenderObjectWidget {
   /// how many frame intervals).
   final int rasterizerThreshold;
 
-  StatisticsBox createRenderObject() => new StatisticsBox(
+  RenderStatisticsBox createRenderObject() => new RenderStatisticsBox(
     optionsMask: optionsMask,
     rasterizerThreshold: rasterizerThreshold
   );
 
-  void updateRenderObject(StatisticsBox renderObject, RenderObjectWidget oldWidget) {
+  void updateRenderObject(RenderStatisticsBox renderObject, RenderObjectWidget oldWidget) {
     renderObject.optionsMask = optionsMask;
     renderObject.rasterizerThreshold = rasterizerThreshold;
   }