Make Drawer in components2 work

sky/sdk/lib/framework/rendering/box.dart

Index: sky/sdk/lib/framework/rendering/box.dart
diff --git a/sky/sdk/lib/framework/rendering/box.dart b/sky/sdk/lib/framework/rendering/box.dart
index 100219477b9e13b750ad812f20c20636e9065313..adb7e455fb6017d0f1dd6e3b39160e263140a35f 100644
--- a/sky/sdk/lib/framework/rendering/box.dart
+++ b/sky/sdk/lib/framework/rendering/box.dart
@@ -50,6 +50,12 @@ class BoxConstraints {
       minHeight = size.height,
       maxHeight = size.height;
 
+  BoxConstraints.loose(sky.Size size)
+    : minWidth = 0.0,
+      maxWidth = size.width,
+      minHeight = 0.0,
+      maxHeight = size.height;
+
   BoxConstraints deflate(EdgeDims edges) {
     assert(edges != null);
     double horizontal = edges.left + edges.right;
@@ -351,9 +357,9 @@ class RenderTransform extends RenderProxyBox {
 
     canvas.save();
     canvas.concat([

[Matt Perry, 2015/06/03 21:29:50]

We could change Canvas.concat to take a Float32List in the format Matrix4 uses.

[Matt Perry, 2015/06/03 22:15:52]

Here's what it would look like:
https://codereview.chromium.org/1155193004/diff/20001/sky/examples/raw/painti...

The question is, should we add our own Matrix class (that maybe just calls
through to the C++ SkMatrix class) to dart:sky, or should we let the framework
handle it (using vector_math.dart like we do here)?

-      storage[ 0], storage[ 1], storage[ 3],
-      storage[ 4], storage[ 5], storage[ 7],
-      storage[12], storage[13], storage[15],

[Hixie, 2015/06/03 21:39:56]

Why doesn't canvas take a Matrix, the same way it takes a Rect for other things?

[abarth-chromium, 2015/06/03 22:33:42]

The answer here is slightly complicated.  The short version is that we're going
to end with two Matrix classes, one that's optimized for manipulation within the
VM and one that's optimized for talking to skia.  Currently the |concat|
function uses neither of these.  Presumably we'll want versions for each one.

+      storage[ 0], storage[ 4], storage[12],
+      storage[ 1], storage[ 5], storage[13],
+      storage[ 3], storage[ 7], storage[15],
     ]);
     super.paint(canvas);
     canvas.restore();