Make the drawer, popup menus, dialogs, and settings page scrollable.

Make the drawer, popup menus, dialogs, and settings page scrollable.

Also, fixes the stocks list to work properly including hit testing at
the bottom of the screen.


New classes:

RenderViewport: a class that supports positioning a child inside
itself and offsetting it.

Viewport: a RenderObjectWrapper that wraps RenderViewport.

ScrollableViewport: a Component that hooks Viewport up to some
scrolling behaviour.


Code changes:

RenderBlock now only works when it has an unbounded height constraint.
I removed the clipping in there since it's no longer needed.

I made FixedHeightScrollable use Viewport instead of hand-rolling its
clipping with Transform and Clip. This is what fixes the stocks list
hit testing at the bottom of the screen.

I made anywhere that used to use Block now use ScrollableViewport.

RenderFlex now takes a list of children.


Justifications for test changes:

tests/examples/stocks: changing FixedHeightScrollable to use a
RenderViewport instead of a RenderClipRect/RenderTransform combination
removes the use of an actual transform.

R=abarth@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/1e65019c0064730142295e8f2d190b5e5ac2fb6c

[abarth-chromium, 2015-07-09 23:39:32]

abarth@chromium.org changed reviewers:
+ abarth@chromium.org

[abarth-chromium, 2015-07-09 23:39:35]

lgtm

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/example/stocks/lib/...
File sky/sdk/example/stocks/lib/stock_settings.dart (right):

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/example/stocks/lib/...
sky/sdk/example/stocks/lib/stock_settings.dart:96: child: new Block([
We should combine these into a ScrollableBlock

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/rendering/box.dart
File sky/sdk/lib/rendering/box.dart (right):

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/rendering/box.d...
sky/sdk/lib/rendering/box.dart:1035: _scrollOffset = value;
Probably should assert that _scrollOffset respects |direction|.  (Also in the
constructor)

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/rendering/box.d...
sky/sdk/lib/rendering/box.dart:1082: innerConstraints = new BoxConstraints();
break;
One statement per line please.

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/rendering/box.d...
sky/sdk/lib/rendering/box.dart:1093: }
Don't we need to size ourselves to something even if we have no child? 
RenderProxyBox calls performResize() to do that (which makes itself as small as
possible).

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/rendering/box.d...
sky/sdk/lib/rendering/box.dart:1097: canvas.clipRect(offset & size);
We should only clip if the child is actually bigger than we are.  (Also, we
shouldn't make an empty clip if we have no child)

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/rendering/objec...
File sky/sdk/lib/rendering/object.dart (right):

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/rendering/objec...
sky/sdk/lib/rendering/object.dart:202: } catch (e, stack) { // TODO(ianh):
Figure out how we can not ask for the stack trace in prod mode
Please don't check this in.

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/rendering/objec...
sky/sdk/lib/rendering/object.dart:356: } catch (e, stack) { // TODO(ianh):
Figure out how we can not ask for the stack trace in prod mode
ditto

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/widgets/scrolla...
File sky/sdk/lib/widgets/scrollable_viewport.dart (right):

https://codereview.chromium.org/1223153004/diff/1/sky/sdk/lib/widgets/scrolla...
sky/sdk/lib/widgets/scrollable_viewport.dart:41: }
You need to check scrollOffset to see if its out-of-bounds

[abarth-chromium, 2015-07-10 23:52:53]

lgtm

[Hixie, 2015-07-10 23:54:23]

Committed patchset #3 (id:40001) manually as
1e65019c0064730142295e8f2d190b5e5ac2fb6c (presubmit successful).