Clean up the tests to be more maintainable.

sky/tests/resources/display_list.dart

Index: sky/tests/resources/display_list.dart
diff --git a/sky/tests/resources/display_list.dart b/sky/tests/resources/display_list.dart
index 7de956b696d2689c487ad090ccf4dbfbe4330180..d831d0412ad736fa2449aed4cca75c3a8b24466e 100644
--- a/sky/tests/resources/display_list.dart
+++ b/sky/tests/resources/display_list.dart
@@ -124,7 +124,7 @@ class TestRenderView extends RenderView {
     attach();
     rootConstraints = new ViewConstraints(width: 800.0, height: 600.0); // arbitrary figures
     scheduleInitialLayout();
-    checkFrame();
+    syncCheckFrame();
   }
 
   int frame = 0;
@@ -147,12 +147,16 @@ class TestRenderView extends RenderView {
 
   // TEST API:
 
-  void checkFrame() {
+  void syncCheckFrame() {
     RenderObject.flushLayout();
     paintFrame();
     print(lastPaint); // TODO(ianh): figure out how to make this fit the unit testing framework better
   }
 
+  Future checkFrame() {
+    return new Future.microtask(syncCheckFrame);
+  }
+
   void endTest() {
     internals.notifyTestComplete("PAINTED $frame FRAMES");
   }
@@ -174,10 +178,10 @@ class WidgetTester {
 
   Future test(Function builder) {
     runApp(new TestApp(builder: builder), renderViewOverride: renderView);
-    return new Future.microtask(renderView.checkFrame);
+    return renderView.checkFrame();
   }
 
-  Future endTest() {
-    return new Future.microtask(renderView.endTest);
+  void endTest() {
+    renderView.endTest();
   }
 }