Rename "Over-scroll" demo to "Pull to refresh" (#8224)

Fixes https://github.com/flutter/flutter/issues/5935

examples/flutter_gallery/lib/gallery/item.dart

@@ -42,6 +42,8 @@ class GalleryItem extends StatelessWidget {
   }
 }
 
+// When editing this list, make sure you keep it in sync with
+// the list in ../../test_driver/transitions_perf_test.dart
 final List<GalleryItem> kAllGalleryItems = <GalleryItem>[
   // Demos
   new GalleryItem(
@@ -162,12 +164,6 @@ final List<GalleryItem> kAllGalleryItems = <GalleryItem>[
     routeName: ModalBottomSheetDemo.routeName,
     buildRoute: (BuildContext context) => new ModalBottomSheetDemo()
   ),
-  new GalleryItem(
-    title: 'Over-scroll',
-    subtitle: 'Refresh and overscroll indicators',
-    routeName: OverscrollDemo.routeName,
-    buildRoute: (BuildContext context) => new OverscrollDemo()
-  ),
   new GalleryItem(
     title: 'Page selector',
     subtitle: 'PageView with indicator',
@@ -186,6 +182,12 @@ final List<GalleryItem> kAllGalleryItems = <GalleryItem>[
     routeName: ProgressIndicatorDemo.routeName,
     buildRoute: (BuildContext context) => new ProgressIndicatorDemo()
   ),
+  new GalleryItem(
+    title: 'Pull to refresh',
+    subtitle: 'Refresh indicators',
+    routeName: OverscrollDemo.routeName,
+    buildRoute: (BuildContext context) => new OverscrollDemo()
+  ),
   new GalleryItem(
     title: 'Scrollable tabs',
     subtitle: 'Tab bar that scrolls',

examples/flutter_gallery/test_driver/transitions_perf_test.dart

@@ -35,10 +35,10 @@ final List<String> demoTitles = <String>[
   'List',
   'Menus',
   'Modal bottom sheet',
-  'Over-scroll',
   'Page selector',
   'Persistent bottom sheet',
   'Progress indicators',
+  'Pull to refresh',
   'Scrollable tabs',
   'Selection controls',
   'Sliders',