Add BoxConstraints.isNormalized feature.
Use this feature in asserts in all the intrinsic dimension methods, in
various relevant BoxConstraints methods, and in layout().
Wrap the _DebugSize logic in BoxConstraints.constrain() in an assert
block to avoid a branch in release mode.
Remove the logic in BoxConstraints.isSatisfiedBy() that dealt with
non-normalized values.
Add BoxConstraints.normalize().
Make RenderCustomOneChildLayoutBox.performLayout() only set
parentUsesSize on the child if the constraints aren't tight.
Instead of PointerInputEvent having a "type" field, we now have a
different class for each pointer type.
This has ripple effects throughout the system.
I also did code cleanup in affected files while I was there.
This patch simplifies PaintingContext with several goals:
1) We now call a callback instead of assuming the caller has a single child to
paint. This change will let us handle render objects that wish to paint more
than one child.
2) We now avoid creating lots of empty picture layers because we don't eagerly
start recording pictures. Instead, we wait for the first caller to touch the
canvas before creating the picture recorder.
3) We now are more consistent about which values have incorporated the painting
offset.
Also, fix warnings in rendering/sector_layout.dart
Also, fix hit testing in rendering/sector_layout.dart
Also, add WidgetToRenderBoxAdapter
Also, make the rendering library debugging tools more resilient to
dumping stuff before layout is complete.
