Using local paths ensures that each package sees each other package at HEAD.

It's common to want a scrolling viewport but with padding around the
contents. Teaching Block about this makes the places that do this
substantially simpler and further buries ScrollableViewport and
BlockBody (they're now only used in scrollable.dart).

More flutter more better.

This patch introduces the notion of a ModalRoute that puts up a modal barrier
and makes the route invisible to hit testing when its animating out. This patch
also uses this mechanism in a number of places (including PageRoute). There are
still a few more cases to convert, but that's work for a future patch.

Fixes #1684

The name of the parameter wasn't consistent with IconButton or DrawerItem, etc.

Fixes #1871

sky_engine is now at 0.0.45
sky_services is now at 0.0.45
flx is now at 0.0.4
flutter is now at 0.0.15
flutter_sprites is now at 0.0.12

sky_engine is now at 0.0.44
sky_services is now at 0.0.44
flx is now at 0.0.3
flutter is now at 0.0.14
flutter_sprites is now at 0.0.11

Material design icons are defined to work at specific sizes: 18, 24, 36, 48.
The current API doesn't reflect that and just takes a size int. If an invalid
size is chosen an error is printed to the console and no icon shows up.

Fixes #1816

- Change RouteArguments to pass the route's BuildContext rather than
  the Navigator. This caused the bulk of the examples/ and .../test/
  changes (those are mostly mechanical changes). It also meant I could
  simplify Navigator.of().

- Make initState() actually get called when the State's Element is in
  the tree, so you can use Foo.of() functions there. Added a test for
  this also.

- Provide a RouteWidget so that routes have a position in the Widget
  tree. The bulk of the route logic is still in a longer-lived Route
  object for now.

- Make Route.setState() only rebuild the actual route, not the whole
  navigator.

- Provided a Route.of().

- Provided a Route.writeState / Route.readState API that tries to
  identify the clients by their runtimeType, their key, and their
  ancestors keys, up to the nearest ancestor with a GlobalKey.

- Made scrollables hook into this API to track state. Added a test to
  make sure this works.

- Fix the debug output of GestureDetector and the hashCode of
  MixedViewport.

- Fixed ScrollableWidgetListState<T> to handle infinite lists.

Instread of an explicit 'enabled' bool, this uses the presence of the
event handler to determine if a widget is enabled or not. This means
that if you've not passed a handler, your widget will be disabled, which
makes sense, since it wouldn't work anyway.

Adds this feature to checkbox, and ports raised button, flat button, and
radio buttons to this new model.

Adds a checkbox to card_collection that can be disabled.

Hide a (basically bogus) hint from the (soon to be disabled) strong hint
mode in the analyzer that this reveals.

If you load the example and immediately switch to the Portfolio tab, you may
see exceptions due to symbols that are in the portfolio list but whose
data is not yet present in the stocks map

Make Radio widgets take a type that describes the type of their value,
so that you can catch when you use the wrong value.

Standardise on ValueChanged<Foo> instead of having a FooValueChanged
for every value of Foo.

Back button wasn't reliably working in checked mode.

This makes skyanalyzer also check the examples, and fixes everything it
found there.

Now you don't need to pass the navigator around everywhere.

The style we use for callbacks in widgets is "onFoo". These classes were using
an order naming convention and just called their callbacks "callback".

Adds a step to the updater to verify that the new .flx package is signed and
untampered.

Each .flx contains a signed manifest file. The manifest contains a SHA-256 hash
of the .flx contents. See bundle.dart for a description of the new .flx format.

Instead of requiring clients to use ui.ColorFilter, we show show the
ColorFilter class, similar to what we do for Color.

We now just use Dart properties, which is more idiomatic.

Fixes #1669

Teach dumpRenderTree() to draw actual trees.
Make the TextStyle output terser so it doesn't overflow the output.
Make debugDumpApp() say what mode we're in (checked vs release).
Hide lifecycle state from release mode dumps (since it's checked-only state).

Add type annotations in many places.
Fix some identifiers to have more lint-satisfying names.
Make all operator==s consistent in style.
Reorder some functions for consistency.
Make ParentData no longer dynamic, and fix all the code around that.

We changed IconButton to require a ColorFilter to filter the color of the icon.

Canvas is by far the most popular type of material by call site (and makes for
a faster default because it doesn't have a RRect clip).

We can build Fitness again now that playfair has been updated to account for
the package:flutter rename.

MaterialApp assumes that you're using material design.

Also move radial reaction and fix imports for stats box.

These are now part of material.dart.

Also, have dialog buttons use the accent colour.
Also, generally rationalise some of this stuff to match Material better.

The margins make using showMenu's menuPosition argument difficult and they're not really needed.

I also made a few small gratuitous changes in navigator.dart.

Rather than using a custom render object, we can just use a Stack.