backgroundColor -> color
backgroundImage -> image
BackgroundImage -> DecorationImage

* Manually fix every use of Point.x and Point.y

Some of these were moved to dx/dy, but not all.

* Manually convert uses of the old gradient API

* Remove old reference to Point.

* Mechanical changes

I applied the following at the root of the Flutter repository:

git ls-files -z | xargs -0 sed -i 's/\bPoint[.]origin\b/Offset.zero/g'
git ls-files -z | xargs -0 sed -i 's/\bPoint[.]lerp\b/Offset.lerp/g'
git ls-files -z | xargs -0 sed -i 's/\bnew Point\b/new Offset/g'
git ls-files -z | xargs -0 sed -i 's/\bconst Point\b/const Offset/g'
git ls-files -z | xargs -0 sed -i 's/\bstatic Point /static Offset /g'
git ls-files -z | xargs -0 sed -i 's/\bfinal Point /final Offset /g'
git ls-files -z | xargs -0 sed -i 's/^\( *\)Point /\1Offset /g'
git ls-files -z | xargs -0 sed -i 's/ui[.]Point\b/ui.Offset/g'
git ls-files -z | xargs -0 sed -i 's/(Point\b/(Offset/g'
git ls-files -z | xargs -0 sed -i 's/\([[{,]\) Point\b/\1 Offset/g'
git ls-files -z | xargs -0 sed -i 's/@required Point\b/@required Offset/g'
git ls-files -z | xargs -0 sed -i 's/<Point>/<Offset>/g'
git ls-files -z | xargs -0 sed -i 's/[.]toOffset()//g'
git ls-files -z | xargs -0 sed -i 's/[.]toPoint()//g'
git ls-files -z | xargs -0 sed -i 's/\bshow Point, /show /g'
git ls-files -z | xargs -0 sed -i 's/\bshow Point;/show Offset;/g'

* Mechanical changes - dartdocs

I applied the following at the root of the Flutter repository:

git ls-files -z | xargs -0 sed -i 's/\ba \[Point\]/an [Offset]/g'
git ls-files -z | xargs -0 sed -i 's/\[Point\]/[Offset]/g'

* Further improvements and a test

* Fix minor errors from rebasing...

* Roll engine

Rename State.config to State.widget
Rename State.didUpdateConfig to State.didUpdateWidget
Renamed all State subclasses' local variables named config to something else

* use color.shadeXxx instead of color[Xxx]

* remove calls to .shade500 on MaterialColor

* remove calls to .shade200 on MaterialAccentColor

* fix test

This patch contains a first draft of an iOS-style switch. We'll likely need to
tweak the constants upon closer study, but the basics are here.

Add some docs to explain how to use setState() wiht Checkbox, Radio,
Slider, and Switch.

Based on experience of usability study participant P1.

This requires all AnimationController objects to be given a
TickerProvider, a class that can create the Ticker.

It also provides some nice mixins for people who want to have their
State provide a TickerProvider. And a schedulerTickerProvider for those
cases where you just want to see your battery burn.

Also, we now enforce destruction order for elements.

We have so many render objects going on these days that showing every
box that gets an event just makes the screen blue. This limits it down
to only the ones that are actually doing something with the events.

* Added custom radii to RRect.

This is the first commit towads an implementation of
MergeableMaterial. It adds custom radii to RRect.

* Renamed RRect constructors and added BorderRadius.

BorderRadius is a class similar to EdgeInsets that lets you define
all rounded corners of a rounded rectangle easily.

Rather than requiring the developer to specify a full Decoration, we now
just take an ImageProvider for the thumb image. Also, fix
ImageFit.scaleDown to actually work.

Fixes #4571
Fixes #4673

I broke them when refactoring images. Oops.

Overview
========

This patch refactors images to achieve the following goals:

* it allows references to unresolved assets to be passed
  around (previously, almost every layer of the system had to know about
  whether an image came from an asset bundle or the network or
  elsewhere, and had to manually interact with the image cache).

* it allows decorations to use the same API for declaring images as the
  widget tree.

It requires some minor changes to call sites that use images, as
discussed below.

Widgets
-------

Change this:

```dart
      child: new AssetImage(
        name: 'my_asset.png',
        ...
      )
```

...to this:

```dart
      child: new Image(
        image: new AssetImage('my_asset.png'),
        ...
      )
```

Decorations
-----------

Change this:

```dart
      child: new DecoratedBox(
        decoration: new BoxDecoration(
          backgroundImage: new BackgroundImage(
            image: DefaultAssetBundle.of(context).loadImage('my_asset.png'),
            ...
          ),
          ...
        ),
        child: ...
      )
```

...to this:

```dart
      child: new DecoratedBox(
        decoration: new BoxDecoration(
          backgroundImage: new BackgroundImage(
            image: new AssetImage('my_asset.png'),
            ...
          ),
          ...
        ),
        child: ...
      )
```

DETAILED CHANGE LOG
===================

The following APIs have been replaced in this patch:

* The `AssetImage` and `NetworkImage` widgets have been split in two,
  with identically-named `ImageProvider` subclasses providing the
  image-loading logic, and a single `Image` widget providing all the
  widget tree logic.

* `ImageResource` is now `ImageStream`. Rather than configuring it with
  a `Future<ImageInfo>`, you complete it with an `ImageStreamCompleter`.

* `ImageCache.load` and `ImageCache.loadProvider` are replaced by
  `ImageCache.putIfAbsent`.

The following APIs have changed in this patch:

* `ImageCache` works in terms of arbitrary keys and caches
  `ImageStreamCompleter` objects using those keys. With the new model,
  you should never need to interact with the cache directly.

* `Decoration` can now be `const`. The state has moved to the
  `BoxPainter` class. Instead of a list of listeners, there's now just a
  single callback and a `dispose()` method on the painter. The callback
  is passed in to the `createBoxPainter()` method. When invoked, you
  should repaint the painter.

The following new APIs are introduced:

* `AssetBundle.loadStructuredData`.

* `SynchronousFuture`, a variant of `Future` that calls the `then`
  callback synchronously. This enables the asynchronous and
  synchronous (in-the-cache) code paths to look identical yet for the
  latter to avoid returning to the event loop mid-paint.

* `ExactAssetImage`, a variant of `AssetImage` that doesn't do anything clever.

* `ImageConfiguration`, a class that describes parameters that configure
  the `AssetImage` resolver.

The following APIs are entirely removed by this patch:

* `AssetBundle.loadImage` is gone. Use an `AssetImage` instead.

* `AssetVendor` is gone. `AssetImage` handles everything `AssetVendor`
  used to handle.

* `RawImageResource` and `AsyncImage` are gone.

The following code-level changes are performed:

* `Image`, which replaces `AsyncImage`, `NetworkImage`, `AssetImage`,
  and `RawResourceImage`, lives in `image.dart`.

* `DecoratedBox` and `Container` live in their own file now,
  `container.dart` (they reference `image.dart`).

DIRECTIONS FOR FUTURE RESEARCH
==============================

* The `ImageConfiguration` fields are mostly aspirational. Right now
  only `devicePixelRatio` and `bundle` are implemented. `locale` isn't
  even plumbed through, it will require work on the localisation logic.

* We should go through and make `BoxDecoration`, `AssetImage`, and
  `NetworkImage` objects `const` where possible.

* This patch makes supporting animated GIFs much easier.

* This patch makes it possible to create an abstract concept of an
  "Icon" that could be either an image or a font-based glyph (using
  `IconData` or similar). (see
  https://github.com/flutter/flutter/issues/4494)

RELATED ISSUES
==============

Fixes https://github.com/flutter/flutter/issues/4500
Fixes https://github.com/flutter/flutter/issues/4495
Obsoletes https://github.com/flutter/flutter/issues/4496

Our track and head were slightly off in size.
These now exactly match the sizes in
https://material.google.com/components/selection-controls.html#selection-controls-switch
We took the liberty of assuming the head overlaps the edge
of the track by 2 pixels (instead of the head and the track ending at the same point)
which the provided designs were conflicted about.

Huge thanks to @DaveShuckerow for noticing this issue!

@abarth

We now use the `@required` annotation to encourage developers to
explicitly set onPressed and onChanged callbacks to null when that would
disable the widget.

Fixes #287

Fixes 3544

Previously we supplied individual parameters to the various drag and pan
callbacks. However, that approach isn't extensible because each new
parameter is a breaking change to the API.

This patch makes a one-time breaking change to the API to provide a
"details" object that we can extend over time as we need to expose more
information. The first planned extension is adding enough information to
accurately produce an overscroll glow on Android.

We weren't listening to the decorations to see when they loaded.

Fixes #4185

It's safe to remove the unneeded `void`s from setters since the blocking issues in the
`always_declare_return_types` lint have been fixed (https://github.com/dart-lang/linter/).  We can also safely flip the bit on  `avoid_return_types_on_setters`.

Fixes #3501

The dartdoc will continue until morale improves.

Also, fill out other documentation for these widgets.

Fixes #967

The touch ripple now starts at the touch location instead of being
centered on the widget.

Fixes #2652

Fixes #2621

This patch renames StatelessComponent to StatelessWidget and
StatefulComponent to StatefulWidget.

Fixes #2308

And fix the zillion issues that uncovered.

This reverts commit f41b3411, reversing
changes made to e33d8d96.

This was a bad check-in due to my mangling uploading a new version of the branch from a different machine.

This reverts https://github.com/flutter/flutter/pull/2639 and will be replaced by https://github.com/flutter/flutter/pull/2640

And fix the zillion issues that uncovered.

We'll need this for RTL support because the RTL state will live in the widget
tree. Also, remove the `oldWidget` argument to updateRenderObject because there
aren't any clients for it.

Fixes #1381

There's no reason to make clients supply a PointerRounter and a
GestureArena when constructing gesture recognizers. These objects are
statics and the gesture recognizers can just grab them directly.

Also, remove the callback constructor arguments. Almost no code used
them. Instead, people seem to prefer using the `..` operator to set
callbacks on the recognizers. Removing the arguments removes a bunch of
boilerplate.

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

Each layer is supposed to reexport the parts of the previous layer
that are part of its API.

- In painting.dart, export from dart:ui all the Canvas-related APIs
  that make sense to be used at higher levels, e.g. PaintingStyle.

- Delete painting/shadows.dart. It was dead code.

- In rendering/object.dart, export all of painting.dart.

- In widgets/basic.dart, export all of painting.dart and
  animation.dart. Some classes in animation/ are renamed to make this
  less disruptive and confusing to the namespace.

- Split out Stocks back into an import model rather than a part model,
  so that it's easier to manage its dependencies on a per-file basis.

- Move Ticker to scheduler library.

- Remove as many redundant imports as possible now.

- Some minor nit picking cleanup in various files.