Optimizes sprites by replacing save/restore by caching the total matrix

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

@@ -37,6 +37,7 @@ class Node {
   int _addedOrder;
   int _childrenLastAddedOrder = 0;
   bool _childrenNeedSorting = false;
+  Matrix4 _savedTotalMatrix;
 
   /// Decides if the node and its children is currently paused.
   ///
@@ -414,7 +415,7 @@ class Node {
   }
 
   void _prePaint(PaintingCanvas canvas) {
-    canvas.save();
+    _savedTotalMatrix = canvas.getTotalMatrix();
 
     // Get the transformation matrix and apply transform
     canvas.concat(transformMatrix.storage);
@@ -465,7 +466,7 @@ class Node {
   }
 
   void _postPaint(PaintingCanvas canvas) {
-    canvas.restore();
+    canvas.setMatrix(_savedTotalMatrix);
   }
 
   // Receiving update calls

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

@@ -65,7 +65,8 @@ class Sprite extends NodeWithSize {
   }
 
   void paint(PaintingCanvas canvas) {
-    canvas.save();
+    // Store old matrix
+    Matrix4 savedMatrix = canvas.getTotalMatrix();
 
     // Account for pivot point
     applyTransformForPivot(canvas);
@@ -107,8 +108,10 @@ class Sprite extends NodeWithSize {
     } else {
       // Paint a red square for missing texture
       canvas.drawRect(new Rect.fromLTRB(0.0, 0.0, size.width, size.height),
-      new Paint()..color = const Color.fromARGB(255, 255, 0, 0));
+      new Paint()..color = new Color.fromARGB(255, 255, 0, 0));
     }
-    canvas.restore();
+
+    // Restore matrix
+    canvas.setMatrix(savedMatrix);
   }
 }