This moves input.dart to editing2/, since that way we can define the layering as strictly unidirectional.
It also reorders a bunch of imports to fit the style guide.
I removed the old remnants of the widgets example, and put the fn2 examples into the examples/widgets/ directory, to parallel the framework directory names.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1177243002.

This also removes one bit of magic to make it more obvious what on is
going on during a sync, which should hopefully help.

Components have to decide if they support being stateful or not. If
they do, then they must implement syncFields() and have mutable
fields; if they don't, then they must have final fields. This isn't
particularly enforced, though.

This also renames _willSync() to _retainStatefulNodeIfPossible(), for
clarity, and fixes some minor style issues and one typo that was
breaking the drawer.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1174023003

This CL does a bunch of ground work for getting StockList ready for use in
stocks2. It's still not quite working because of an interaction with Scaffold
that we don't fully understand.

R=eseidel@chromium.org, ianh@google.com

Review URL: https://codereview.chromium.org/1148793005

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1153223003

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1156543004

Revert "Add library names to many sky libraries"

This reverts commit 1337e0a803a54ee92d6dce7f8c4a6335f7cbb9fa.

BUG=
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1142893007

- Analyzer complains about libraries not having names. This adds names to many libraries.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1150433002

remove members that are never read
remove imports that are never used

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1099203002

- make the ScrollBehavior instance long-lived, rather than recreating
  it each time we update the list contents.
- have OverscrollBehavior track the total height of the contents and
  the height of the scrollable region, so that it can determine when
  to stop scrolling down.
- teach OverscrollBehavior about how to determine when to stop
  scrolling down, and how to bounce when it's too far down.
- replace the 'energy' concept in Particles with a method that sets
  the energy and direction at the same time, instead of assuming that
  the direction is always positive when setting energy.
- make FixedHeightScrollable lists track the number of items in the
  list and have them update their ScrollBehavior regarding this
  information as it changes.
- track how many items are currently showing in the list stock list.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1097373002

[Effen] Only skip rows we're showing, when skipping past the rows that we've scrolled beyond in the stock list.

Currently, if you then scroll down N items with a filter set, we select which
stock to show by taking the entire list of stocks, skipping the first N, then
filtering the list, then selecting as many stocks as needed to fill the list.

So suppose the list is A, B, Cx, Dx, Ex, F, and the filter is "x", and you've
scrolled down 1 item.

Currently we'd show Cx, Dx, Ex.

Scroll down 1 again.

We still show Cx, Dx, Ex.

What we _should_ show is Dx, Ex if you've scrolled down 1, and just Ex if you've
scrolled two.

This patch fixes this. We now skip rows _after_ filtering. This fixes
the bug whereby if you set a filter then fling the list, we show the
same item over and over as if in a loop.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1057603006

R=eseidel@chromium.org

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

1) Merge input example into widgets example
2) Move single-file, non-fn examples into a "raw" directory
3) Rename stocks-fn and widgets-fn to stocks and widgets

R=ojan@chromium.org

Review URL: https://codereview.chromium.org/1005393006

1) Add a pubspec.yaml.
2) Move all the code into a 'lib' directory.
3) Move the stock widgets out of the app's library.

TBR=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1011023003

This CL cleans up the sky/framework/animation as follows:

1) I've moved code that's used only by the custom elements framework into
   sky/framework/elements/animation. This code is based on AnimationDelegates
   rather than Streams.
2) Rename ScrollCurve to ScrollBehavior because it encapsulates more behavior
   than just a curve.
3) Make the Generator interface explicit and mark subclasses as actual
   subclasses.
4) Move Simulation into generators.dart because it implements the Generator
   interface.
5) Move Animation out of generators.dart because it does not implement the
   Generator interface.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1001373002

When using OverscrollCurve, we continue to scroll beyond the top of the
scrollable area but the scroll delta is reduced by 2x. A future CL will add an
animation at gesturescrollend to relax back to scroll position 0.0.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1002953003

Intead of hard-coding the notion of bounded scrolling into Scrollable, this CL
factors out a ScrollCurve class that applies the bounds. In the future, we'll
refine this mechanism to implement overflow scrolling.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1005633002

We don't yet reset the scroll offset, so sometimes you can't see your search
results properly.

R=rafaelw@chromium.org

Review URL: https://codereview.chromium.org/1002453003

"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

Ensure that sky Nodes are in the document when didMount() is fired. Refactor FixedHeightScrollable to inspect heights rather than having the passed in

BUG=
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/994553003

This is just a proof of concept. If we like this direction, it will move out of the examples directory (likely re-written) and be committed in smaller pieces with unit tests and formal reviews.

TBR=abarth
BUG=

Review URL: https://codereview.chromium.org/971183002