NOTE: This CL appears far larger than it actually is for two reasons:

1) Many files were moved around to use the Dart package directory structure.
2) Many .dart files had to have import paths updated.

- Organize mojo/public/dart so that it uses standard Dart package layout
- Organize mojo/dart/apptest so that it uses a standard Dart package layout
- Organize sky/sdk so that it uses a standard Dart package layout
- Create a mojo/testing package (used by unittests)
- Introduce the 'dart_pkg' gn rule which populates gen/Config/dart-pkg
- All internally vended Dart packages must have a corresponding dart_pkg rule
- It is now possible to use dependency_overrides: in pubspec.yaml to mix internal and external package dependencies (enables analyzer, editor, webstorm usage for internal developers).
- Package root for dart content handler ends with "packages/"
- Imports of mojo package uris no longer need the "public/dart"
- mojo/public/tools/dart_package.py is a clone of mojo/public/tools/gn/zip.py
- Sky tests no longer run 'deploy_sdk' script.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1132063007

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1104233003

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1043283003

Most of the elements that want to be Material (i.e., have a level and cast a
shadow) don't want to be InkWells (i.e., have an ink splash effect). This CL
disentangles these two components, fixing bugs in the Drawer and in the
PopupMenu. Separating these concepts also lets us use Material for the
ActionBar and the FloatingActionButton.

R=rafaelw@chromium.org

Review URL: https://codereview.chromium.org/1037673002

There's no reason for Material to take a |style| parameter anymore. Clients can
simply use StyleNode instead.

R=rafaelw@chromium.org

Review URL: https://codereview.chromium.org/1030963005

There's no reason for InkWell to take a |style| parameter anymore. Clients can
simply use StyleNode instead.

R=rafaelw@chromium.org

Review URL: https://codereview.chromium.org/1019443003

1) Factors InkWell out of Material so that components can use an ink well
   without needing the shadow/level machinery.

2) Makes the ink effect move at a different velocity once the tap has actually
   occurred, converging with the spec. We don't have the right speeds yet, but
   at least we're approaching the right shape.

3) To support (2), added a primaryPointer attribute to GestureEvents to let
   authors coorelate gesturetapdown events with later gesturetap events.

4) To support (2), modernized SplashAnimation to used AnimatedValue and friends.

5) Added more constants to view-configuration.dart that match Android.

I've also removed the cancelling of the ink effect on scroll. The proper way to
do that is to notice that someone in the event chain is listening for
scrollstart and delay the beginning of the ink effect for some period of time.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1019023003

This patch removes the mutable API to event handling (Nodes no longer have a events object with which to add listeners).

Instead, a new (non-Render) Node is introduced: EventTarget. This node represents a location in the Effen tree which can handle events as they bubble.

Note that this also changes the implementation to use event delegation (one set of listeners at the sky.document level) rather than direct listeners on leaf nodes.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1019633004

This CL is a warmup for using a more sophisticated gesture disambiguation.

1) Use gesturetap instead of click. We should probably remove click events
   because folks should use gesturetap to integrate with the gesture system.

2) Handle the case where you swipe the drawer during an animation. Previously
   we had an assert which triggered in some multitouch scenarios. We'll
   eventually move this over to gestureswipe.

3) Remove an extra container for ink splashes. There's no need to group all the
   ink splashes in a container. They can all just be children of the Material
   component itself. This structure is left over from when Material was a base
   class.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1013713005

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1006053002

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1000863002

To accomplish this, I made the following changes:

1) Material is now in charge of drawing the material shadows.
2) In order to mix in the style for the shadow, Element now takes a list of
   Styles instead of a single style.
3) Update all clients of Element#style to understand that we now have a list.
4) Update components that drawer shadows to have Material do that work instead.
   a) One exception: FloatingActionButton draws its own shadow because of its
      crazy clip requirements. We'll probably want to find a better way for
      FloatingActionButton to clip in the future.

I've also added a widgets-fn example to demo the fn material widgets.

This CL introduces a bug into Drawer whereby you can get ink splashes
everywhere in the drawer. In the future, we'll need to separate out the
different material aspects to get non-splashable materials.

R=rafaelw@chromium.org

Review URL: https://codereview.chromium.org/1003553002

Instead of MaterialComponent being a base class, components that want material
behavior simply create a MaterialComponent during their render function. This
approach gives the component more flexibility as to its structure and gives
MaterialComponent more flexibility has to how the components it generates are
related to the existing children.

Also, I've improved some of the event delegation code. There's no reason to
attach event handlers to the root component you emit during |render| because
the framework already delegates events from your root component to you.

R=rafaelw@chromium.org

Review URL: https://codereview.chromium.org/983903003

Moving these files into sky/framework will make them easier to use from the
SDK. Also, this CL also splits up the giant "widgets" library into smaller
libraries, one per component.

TBR=eseidel@chromium.org

Review URL: https://codereview.chromium.org/993033003

"Render" is misleading. "Build" may not be the best word either, it's closer to what's actually happening.

R=ojan@chromium.org
TBR=abarth
BUG=

Review URL: https://codereview.chromium.org/992033002

This patch changes the timing of the unmount call until after the component is removed (and marked as such) and allows setState to be called after this point. If this happens, setState will still invoke the closer to do any neccesary cleanup, but doesn't schedule the component for render

R=eseidel@chromium.org, eseidel
BUG=

Review URL: https://codereview.chromium.org/985853002

To test:
sky/tools/shelldb analyze sky/examples/stocks-fn/stocksapp.dart

It prints 600+ warnings about the "native" keyword, and after
this change only a couple warnings about missing library names
which I don't fully understand.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/987613002

This CL changes how events work in fn. Previously, event listeners were passed
in as constructor arguments. Now Nodes hold an |events| object, which contains
all the event registrations. When a Component renders, all its |events| are
copied onto the Node it produces. When an Element syncs, it walks its |events|
and adds them as event listeners on the underlying sky.Element.

The net result of this change is increased flexibility in how events are
registered. Now components don't need to enumerate all the possible events that
they support. Instead, the parent component can listen for whatever events it
likes.

Also, I've cleaned up the association between DrawerAnimation and Drawer. Now
the constructor for Drawer accepts an |animation| object and wires up its
internal event handlers itself instead of requiring the constructor to do all
the wiring.

R=rafaelw@chromium.org

Review URL: https://codereview.chromium.org/975863003

TBR=raf

Review URL: https://codereview.chromium.org/974903005