Remove RenderView.paintFrame

We now use the repaint system to do all the painting. During initialization, we
set up a root layer that applies the device pixel ratio.

Fixes #706

packages/flutter/lib/rendering/layer.dart

@@ -169,6 +169,19 @@ class ContainerLayer extends Layer {
     child._parent = null;
   }
 
+  void removeAllChildren() {
+    Layer child = _firstChild;
+    while (child != null) {
+      Layer next = child.nextSibling;
+      child._previousSibling = null;
+      child._nextSibling = null;
+      child._parent = null;
+      child = next;
+    }
+    _firstChild = null;
+    _lastChild = null;
+  }
+
   void paint(sky.Canvas canvas) {
     canvas.translate(offset.dx, offset.dy);
     paintChildren(canvas);

packages/flutter/lib/rendering/object.dart

@@ -51,13 +51,6 @@ class PaintingContext {
     _startRecording(paintBounds);
   }
 
-  factory PaintingContext.replacingLayer(ContainerLayer oldLayer, Rect paintBounds) {
-    PaintingContext newContext = new PaintingContext.withOffset(oldLayer.offset, paintBounds);
-    if (oldLayer.parent != null)
-      oldLayer.replaceWith(newContext._containerLayer);
-    return newContext;
-  }
-
   PaintingContext.forTesting(this._canvas);
 
   ContainerLayer _containerLayer;
@@ -650,21 +643,20 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
       sky.tracing.end('RenderObject.flushPaint');
     }
   }
-  void initialPaint(ContainerLayer rootLayer, Size size) {
+  void scheduleInitialPaint(ContainerLayer rootLayer) {
     assert(attached);
     assert(parent is! RenderObject);
     assert(!_debugDoingPaint);
     assert(hasLayer);
-    PaintingContext newContext = new PaintingContext.withLayer(rootLayer, Point.origin & size);
-    _paintLayer(newContext);
+    _layer = rootLayer;
+    assert(_needsPaint);
+    _nodesNeedingPaint.add(this);
   }
   void _repaint() {
     assert(hasLayer);
     assert(_layer != null);
-    PaintingContext newContext = new PaintingContext.replacingLayer(_layer, paintBounds);
-    _paintLayer(newContext);
-  }
-  void _paintLayer(PaintingContext context) {
+    _layer.removeAllChildren();
+    PaintingContext context = new PaintingContext.withLayer(_layer, paintBounds);
     _layer = context._containerLayer;
     try {
       _paintWithContext(context, Offset.zero);

packages/flutter/lib/rendering/sky_binding.dart

@@ -44,6 +44,7 @@ class SkyBinding {
       _renderView.attach();
       _renderView.rootConstraints = _createConstraints();
       _renderView.scheduleInitialLayout();
+      _renderView.initializeLayerTree();
     } else {
       _renderView = renderViewOverride;
     }
@@ -74,7 +75,6 @@ class SkyBinding {
     RenderObject.flushLayout();
     _renderView.updateCompositingBits();
     RenderObject.flushPaint();
-    _renderView.paintFrame();
     _renderView.compositeFrame();
   }
 

packages/flutter/lib/rendering/view.dart

@@ -42,6 +42,12 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
     markNeedsLayout();
   }
 
+  void initializeLayerTree() {
+    final double devicePixelRatio = sky.view.devicePixelRatio;
+    Matrix4 logicalToDeviceZoom = new Matrix4.diagonal3Values(devicePixelRatio, devicePixelRatio, 1.0);
+    scheduleInitialPaint(new TransformLayer(transform: logicalToDeviceZoom));
+  }
+
   // We never call layout() on this class, so this should never get
   // checked. (This class is laid out using scheduleInitialLayout().)
   bool debugDoesMeetConstraints() { assert(false); return false; }
@@ -84,18 +90,6 @@ class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox>
       context.paintChild(child, offset.toPoint());
   }
 
-  void paintFrame() {
-    sky.tracing.begin('RenderView.paintFrame');
-    try {
-      final double devicePixelRatio = sky.view.devicePixelRatio;
-      Matrix4 logicalToDeviceZoom = new Matrix4.diagonal3Values(devicePixelRatio, devicePixelRatio, 1.0);
-      ContainerLayer rootLayer = new TransformLayer(transform: logicalToDeviceZoom);
-      initialPaint(rootLayer, size);
-    } finally {
-      sky.tracing.end('RenderView.paintFrame');
-    }
-  }
-
   void compositeFrame() {
     sky.tracing.begin('RenderView.compositeFrame');
     try {