Merge pull request #595 from Hixie/trivial-cleanup

Fix minor typos and style nits.

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

@@ -284,9 +284,9 @@ class PaintingContext {
       childContext._stopRecordingIfNeeded();
     } else {
       Matrix4 offsetMatrix = new Matrix4.translationValues(offset.dx, offset.dy, 0.0);
-      Matrix4 trasnformWithOffset = offsetMatrix * transform;
+      Matrix4 transformWithOffset = offsetMatrix * transform;
       canvas.save();
-      canvas.concat(trasnformWithOffset.storage);
+      canvas.concat(transformWithOffset.storage);
       painter(this, Offset.zero);
       canvas.restore();
     }
@@ -515,7 +515,7 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
     while (node != _relayoutSubtreeRoot) {
       assert(node._relayoutSubtreeRoot == _relayoutSubtreeRoot);
       assert(node.parent != null);
-      node = node.parent as RenderObject;
+      node = node.parent;
       if ((!node._needsLayout) && (!node._debugDoingThisLayout))
         return false;
     }
@@ -1083,7 +1083,7 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
       int count = 1;
       RenderObject target = parent;
       while (target != null && target != _relayoutSubtreeRoot) {
-        target = target.parent as RenderObject;
+        target = target.parent;
         count += 1;
       }
       header += ' relayoutSubtreeRoot=up$count';

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

@@ -121,10 +121,12 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
   void compositeFrame() {
     Timeline.startSync('Composite');
     try {
-      (layer as TransformLayer).transform = _logicalToDeviceTransform;
+      final TransformLayer transformLayer = layer;
+      transformLayer.transform = _logicalToDeviceTransform;
       Rect bounds = Point.origin & (size * ui.window.devicePixelRatio);
       ui.SceneBuilder builder = new ui.SceneBuilder(bounds);
-      layer.addToScene(builder, Offset.zero);
+      transformLayer.addToScene(builder, Offset.zero);
+      assert(layer == transformLayer);
       ui.Scene scene = builder.build();
       ui.window.render(scene);
       scene.dispose();