Document the onPressed/disabled behavior.

Fixes https://github.com/flutter/flutter/issues/1331

Hopefully this will be enough to start with. If this continues to be a
point of confusion we can see about adding more documentation or
changing the API somehow.

Rename debugDescribeSettings to debugFillDescription.

Add a Velocity class to be explicit about units

...so that it's easier to copy/paste between the rendering and settings layers.

We were using an Offset, which represented pixels/second, but it wasn't
clear to clients whether that was pixels/ms. Now we use a Velocity class
that is explict about the units.

Fixes #1510
Fixes #785

Fix infra docs

Previously we had the wrong path to the recipes.py script and an incorrect argument list.

Use Image.toString instead of rolling our own each time

Add a raw hello_world that shows "Hello, world"

I meant to check this in as part of https://github.com/flutter/flutter/pull/1852
but forgot to commit the local change, d'oh.

Fix color of icons in drawers in dark theme.

Disable flakey test.

See https://github.com/flutter/flutter/issues/1854

This makes it match the material spec more.
https://www.google.com/design/spec/style/icons.html

Fixes https://github.com/flutter/flutter/issues/1357

Previously, hello_world.dart was an interactive circle. I've moved that
to touch_input.dart. We should eventually harmonize the touch input
examples at all the layers.

Adds documentation to the layering examples

allow any android sdk version

This library is being folded into dart:ui.

Fixes #83

Clean up the standalone examples

Our examples have been growing organically over time. This patch cleans
them up to illustrate specific aspects of Flutter.

@abarth

SawTooth

SizeObserver crusade: drawer

Horizontal and Vertical Draggables

Don’t require global keys for Input, fixes #1828

Drawer doesn't need a SizeObserver, since it only looks at the size
in event handlers. It can just go and probe the tree to read the size.

Also, change from using _kEdgeDragWidth to using _kWidth when figuring
out how much of the drawer to show when dragging it from the edge, since
that is more likely to match the drawer's width.

Expose more debugging tools in Stocks

Use mojo's scripts for downloading android tools on the bots

R=abarth@chromium.org

Remove address_book and mine_digger

These examples aren't particularly good models for new Flutter apps.

Bump the flutter_gallery_assets version, rename example apk dirs to android, remove BUILD.gn files