All the use cases for EventDisposition are now addressed by the gesture
detection system.

We no longer have gesture events.

Add a LeafRenderObjectElement, fix a test to use the new contract.

- adds dartdocs
- replaces config setter with didUpdateConfig() so that you can't replace
the config outside of the system
- renames didUnmount() with destroy().
- rename Component to StatelessComponent, ComponentConfiguration to
StatefulComponent
- move debug dump to end of file
- renamed _holder to _element

fn3 shouldn't rebuild components that don't change identity

add a test for scale gestures

Previously --stage-two would error out because the LICENSE was git ignored.
This patch includes the LICENSE file in the repo to avoid the error. Also,
refactor the big_red_button.py to be clearer about what's shared between stage
one and stage two of the release process.

Prototype of fn3

We were just missing a few type casts in tests to make the analyzer happy.

This patch contains a prototype of a new widget framework. In this framework,
Components can be reused in the tree as many times as the author desires. Also,
StatefulComponent is split into two pieces, a ComponentConfiguration and a
ComponentState. The ComponentConfiguration is created by the author and can be
reused as many times as desired. When mounted into the tree, the
ComponentConfiguration creates a ComponentState to hold the state for the
component. The state remains in the tree and cannot be reused.

Instead of having to manage the popup menu from your app's build
function, you now just call showPopupMenu() with the menu's position and
it takes care of everything for you.

This solves the problem that the popup menu was trying to mutate the
state of the navigator from within its own initState() function.

Also, remove the "route" argument to RouteBase.build() since it equals
"this" by definition...

Also, remove ModalOverlay, and instead put that logic in the navigator.

Improvements to EffectLine in sprites

Move findAncestorRenderObjectWrapper to RenderObjectWrapper

Fix Rect intersection; add test

That way it's closer to where it's used, and it's more obvious that
anyone can write such functions.

- Fix AnimationTiming to have defaults for 'interval' and 'curve' since
  that seems to be how we use it.

- Merge RouteBase.build and RouteBase.buildTransition

- Get rid of HistoryEntry, since it added nothing

- Broke out RouteBase.createPerformance() so subclasses can change what
  is created.

- Build the routes backwards so that we more efficiently avoid building
  hidden routes.

- Introduce an explicit way (!hasContent) for RouteState to avoid
  building, rather than the implicit "build returns null" we had before.

In EditableText, wrap the placeholder text in a Row so it will expand to its parent's width

This will ensure that the width of an empty Input is consistent with the
width of an Input that contains text.

Also add a unit test for the Input widget and a way for tests to provide mock
implementations of Mojo services such as the keyboard.

SkySprites should import the public libraries

Require that you pass transitions a performance.

Importing the public libraries caused a name conflict with dart:sky because we
assume people will import dart:sky into a namespace, so I've also changed
skysprites to import dart:sky into a namespace.

I've also removed the top-level description of the Sky package. Instead, we
should host that content on flutter.io.

This fixes #1103.

This might be helpful for #1219.

Also, remove inDebugMode since it's redundant with just using asserts,
which compile entirely out in release mode.

Also, introduce Colors and Typography to hold the material colors and the
typography declarations. Previously we expected clients of these libraries to
import them into a namespace, but that doesn't play nice with re-exporting them
from material.dart.

When we sync() a Component, we need to clear the old Component's _child
pointer, otherwise if we reuse that Component we'll get confused about
what the old child is.

Improve debugging aids for widgets, rendering.

Kill the sky_server on Mac in a way that works to avoid unexpected behavior when working with more than one app at once.

Remove the skyx package

This code is now part of sky_tools.