Fixes compilation errors in sprites

packages/flutter/example/game/lib/node.dart

@@ -416,7 +416,7 @@ class Node {
   }
 
   void _prePaint(PaintingCanvas canvas) {
-    _savedTotalMatrix = canvas.getTotalMatrix();
+    _savedTotalMatrix = new Matrix4.fromFloat32List(canvas.getTotalMatrix());;
 
     // Get the transformation matrix and apply transform
     canvas.concat(transformMatrix.storage);
@@ -467,7 +467,7 @@ class Node {
   }
 
   void _postPaint(PaintingCanvas canvas) {
-    canvas.setMatrix(_savedTotalMatrix);
+    canvas.setMatrix(_savedTotalMatrix.storage);
   }
 
   // Receiving update calls

packages/flutter/example/game/lib/sprite.dart

@@ -68,7 +68,7 @@ class Sprite extends NodeWithSize {
 
   void paint(PaintingCanvas canvas) {
     // Store old matrix
-    Matrix4 savedMatrix = canvas.getTotalMatrix();
+    Matrix4 savedMatrix = new Matrix4.fromFloat32List(canvas.getTotalMatrix());
 
     // Account for pivot point
     applyTransformForPivot(canvas);
@@ -113,6 +113,6 @@ class Sprite extends NodeWithSize {
     }
 
     // Restore matrix
-    canvas.setMatrix(savedMatrix);
+    canvas.setMatrix(savedMatrix.storage);
   }
 }