Instead of applying a transform for every RenderObject, pass down an Offset for where to paint.

sky/sdk/lib/rendering/box.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 
 import 'package:vector_math/vector_math.dart';
 
 import '../base/debug.dart';
@@ skipping 411 matching lines @@
     }
   }
 
   void hitTestChildren(HitTestResult result, { Point position }) {
     if (child != null)
       child.hitTest(result, position: position);
     else
       super.hitTestChildren(result, position: position);
   }
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     if (child != null)
-      child.paint(canvas);
+      child.paint(canvas, offset);
   }
 
 }
 
 class RenderConstrainedBox extends RenderProxyBox {
   RenderConstrainedBox({
     RenderBox child,
     BoxConstraints additionalConstraints
   }) : super(child), _additionalConstraints = additionalConstraints {
     assert(additionalConstraints != null);
@@ skipping 98 matching lines @@
   double get opacity => _opacity;
   void set opacity (double value) {
     assert(value != null);
     assert(value >= 0.0 && value <= 1.0);
     if (_opacity == value)
       return;
     _opacity = value;
     markNeedsPaint();
   }
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     if (child != null) {
       int a = (_opacity * 255).round();
 
       if (a == 0)
         return;
 
       if (a == 255) {
-        child.paint(canvas);
+        child.paint(canvas, offset);
         return;
       }
 
       Paint paint = new Paint()
         ..color = new Color.fromARGB(a, 0, 0, 0)
         ..setTransferMode(sky.TransferMode.srcOver);
       canvas.saveLayer(null, paint);
-      child.paint(canvas);
+      child.paint(canvas, offset);
       canvas.restore();
     }
   }
 }
 
 class RenderColorFilter extends RenderProxyBox {
   RenderColorFilter({ RenderBox child, Color color, sky.TransferMode transferMode })
     : _color = color, _transferMode = transferMode, super(child) {
   }
 
@@ skipping 10 matching lines @@
   sky.TransferMode _transferMode;
   sky.TransferMode get transferMode => _transferMode;
   void set transferMode (sky.TransferMode value) {
     assert(value != null);
     if (_transferMode == value)
       return;
     _transferMode = value;
     markNeedsPaint();
   }
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     if (child != null) {
       Paint paint = new Paint()
         ..setColorFilter(new sky.ColorFilter.mode(_color, _transferMode));
       canvas.saveLayer(null, paint);
-      child.paint(canvas);
+      child.paint(canvas, offset);
       canvas.restore();
     }
   }
 }
 
 class RenderClipRect extends RenderProxyBox {
   RenderClipRect({ RenderBox child }) : super(child);
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     if (child != null) {
       canvas.save();
-      canvas.clipRect(new Rect.fromSize(size));
-      child.paint(canvas);
+      canvas.clipRect(offset + size);
+      child.paint(canvas, offset);
       canvas.restore();
     }
   }
 }
 
 class RenderClipRRect extends RenderProxyBox {
   RenderClipRRect({ RenderBox child, double xRadius, double yRadius })
     : _xRadius = xRadius, _yRadius = yRadius, super(child) {
     assert(_xRadius != null);
     assert(_yRadius != null);
@@ skipping 12 matching lines @@
   double _yRadius;
   double get yRadius => _yRadius;
   void set yRadius (double value) {
     assert(value != null);
     if (_yRadius == value)
       return;
     _yRadius = value;
     markNeedsPaint();
   }
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     if (child != null) {
-      Rect rect = new Rect.fromSize(size);
+      Rect rect = offset + size;

[abarth-chromium, 2015/06/27 00:39:37]

This looks really slick, but I wonder if it's going to be confusing later. 
Maybe operator* would be clearer?

       canvas.saveLayer(rect, new Paint());
       sky.RRect rrect = new sky.RRect()..setRectXY(rect, xRadius, yRadius);
       canvas.clipRRect(rrect);
-      child.paint(canvas);
+      child.paint(canvas, offset);
       canvas.restore();
     }
   }
 }
 
 class RenderClipOval extends RenderProxyBox {
   RenderClipOval({ RenderBox child }) : super(child);
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     if (child != null) {
-      Rect rect = new Rect.fromSize(size);
+      Rect rect = offset + size;
       canvas.saveLayer(rect, new Paint());
       Path path = new Path();
       path.addOval(rect);
       canvas.clipPath(path);
-      child.paint(canvas);
+      child.paint(canvas, offset);
       canvas.restore();
     }
   }
 }
 
 abstract class RenderShiftedBox extends RenderBox with RenderObjectWithChildMixin<RenderBox> {
 
   // Abstract class for one-child-layout render boxes
 
   RenderShiftedBox(RenderBox child) {
     this.child = child;
   }
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     if (child != null)
-      canvas.paintChild(child, child.parentData.position);
+      canvas.paintChild(child, child.parentData.position + offset);
   }
 
   double getDistanceToActualBaseline(TextBaseline baseline) {
     double result;
     if (child != null) {
       assert(!needsLayout);
       result = child.getDistanceToActualBaseline(baseline);
       assert(child.parentData is BoxParentData);
       if (result != null)
         result += child.parentData.position.y;
@@ skipping 227 matching lines @@
   }
 
   double getMaxIntrinsicHeight(BoxConstraints constraints) {
     return _sizeForConstraints(constraints).height;
   }
 
   void performLayout() {
     size = _sizeForConstraints(constraints);
   }
 
-  void paint(RenderCanvas canvas) {
-    if (_image == null) return;
+  void paint(RenderCanvas canvas, Offset offset) {
+    if (_image == null)
+      return;
     bool needsScale = size.width != _image.width || size.height != _image.height;
     if (needsScale) {
       double widthScale = size.width / _image.width;
       double heightScale = size.height / _image.height;
       canvas.save();
+      canvas.translate(offset.dx, offset.dy);
       canvas.scale(widthScale, heightScale);
+      offset = Offset.zero;
     }
     Paint paint = new Paint();
-    canvas.drawImage(_image, Point.origin, paint);
+    canvas.drawImage(_image, offset.toPoint(), paint);
     if (needsScale)
       canvas.restore();
   }
 
   String debugDescribeSettings(String prefix) => '${super.debugDescribeSettings(prefix)}${prefix}url: ${src}\n${prefix}dimensions: ${requestedSize}\n';
 }
 
 class RenderDecoratedBox extends RenderProxyBox {
 
   RenderDecoratedBox({
     BoxDecoration decoration,
     RenderBox child
   }) : _painter = new BoxPainter(decoration), super(child);
 
   BoxPainter _painter;
   BoxDecoration get decoration => _painter.decoration;
   void set decoration (BoxDecoration value) {
     assert(value != null);
     if (value == _painter.decoration)
       return;
     _painter.decoration = value;
     markNeedsPaint();
   }
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     assert(size.width != null);
     assert(size.height != null);
-    _painter.paint(canvas, new Rect.fromSize(size));
-    super.paint(canvas);
+    _painter.paint(canvas, offset + size);
+    super.paint(canvas, offset);
   }
 
   String debugDescribeSettings(String prefix) => '${super.debugDescribeSettings(prefix)}${prefix}decoration:\n${_painter.decoration.toString(prefix + "  ")}\n';
 }
 
 class RenderTransform extends RenderProxyBox {
   RenderTransform({
     Matrix4 transform,
     RenderBox child
   }) : super(child) {
@@ skipping 45 matching lines @@
     Matrix4 inverse = new Matrix4.zero();
     /* double det = */ inverse.copyInverse(_transform);
     // TODO(abarth): Check the determinant for degeneracy.
 
     Vector3 position3 = new Vector3(position.x, position.y, 0.0);
     Vector3 transformed3 = inverse.transform3(position3);
     Point transformed = new Point(transformed3.x, transformed3.y);
     super.hitTestChildren(result, position: transformed);
   }
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     canvas.save();
+    canvas.translate(offset.dx, offset.dy);
     canvas.concat(_transform.storage);
-    super.paint(canvas);
+    super.paint(canvas, Offset.zero);
     canvas.restore();
   }
 
   String debugDescribeSettings(String prefix) {
     List<String> result = _transform.toString().split('\n').map((s) => '$prefix  $s\n').toList();
     result.removeLast();
     return '${super.debugDescribeSettings(prefix)}${prefix}transform matrix:\n${result.join()}';
   }
 }
 
@@ skipping 38 matching lines @@
       return;
     _callback = value;
     markNeedsPaint();
   }
 
   void attach() {
     assert(_callback != null);
     super.attach();
   }
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     assert(_callback != null);
+    canvas.translate(offset.dx, offset.dy);
     _callback(canvas, size);
-    super.paint(canvas);
+    super.paint(canvas, Offset.zero);
+    canvas.translate(-offset.dx, -offset.dy);

[abarth-chromium, 2015/06/27 00:39:37]

It's a shame that custom paint callbacks need to pay this penalty.  It's
probably worth it for programming simplicity though.

   }
 }
 
 // RENDER VIEW LAYOUT MANAGER
 
 class ViewConstraints {
   const ViewConstraints({
     this.size: Size.zero,
     this.orientation
   });
@@ skipping 50 matching lines @@
   bool hitTest(HitTestResult result, { Point position }) {
     if (child != null) {
       Rect childBounds = new Rect.fromSize(child.size);
       if (childBounds.contains(position))
         child.hitTest(result, position: position);
     }
     result.add(new HitTestEntry(this));
     return true;
   }
 
-  void paint(RenderCanvas canvas) {
+  void paint(RenderCanvas canvas, Offset offset) {
     if (child != null)
-      canvas.paintChild(child, Point.origin);
+      canvas.paintChild(child, offset.toPoint());
   }
 
   void paintFrame() {
     sky.tracing.begin('RenderView.paintFrame');
     RenderObject.debugDoingPaint = true;
     try {
       sky.PictureRecorder recorder = new sky.PictureRecorder();
       RenderCanvas canvas = new RenderCanvas(recorder, _size);
-      paint(canvas);
+      paint(canvas, Offset.zero);
       sky.view.picture = recorder.endRecording();
     } finally {
       RenderObject.debugDoingPaint = false;
       sky.tracing.end('RenderView.paintFrame');
     }
   }
 
 }
 
 // HELPER METHODS FOR RENDERBOX CONTAINERS
@@ skipping 42 matching lines @@
       Rect childBounds = new Rect.fromPointAndSize(child.parentData.position, child.size);
       if (childBounds.contains(position)) {
         if (child.hitTest(result, position: new Point(position.x - child.parentData.position.x,
                                                           position.y - child.parentData.position.y)))
           break;
       }
       child = child.parentData.previousSibling;
     }
   }
 
-  void defaultPaint(RenderCanvas canvas) {
+  void defaultPaint(RenderCanvas canvas, Offset offset) {
     RenderBox child = firstChild;
     while (child != null) {
       assert(child.parentData is ParentDataType);
-      canvas.paintChild(child, child.parentData.position);
+      canvas.paintChild(child, child.parentData.position + offset);
       child = child.parentData.nextSibling;
     }
   }
 }