I'll write the Widget wrapper in the next CL, including adding
support for padding at the Widget layer.

@Hixie

We need to implement visitChildren for the RenderObjects in the sector demo.
Also, add a test.

Fixes #790

This still leaves Flex and FlexDirection available. At some point once
people have transitioned to Row/Column we should rename Flex to _Flex
and stop reexporting FlexDirection from basic.dart.

Fixes #743

Similar to widgets.dart, rendering.dart exports the entire rendering layer.
Also, update the examples to use rendering.dart and widgets.dart. Also clean up
some exports so that the examples have more sensible imports.

Sadly, box.dart has grown much longer than 1000 lines. This patch splits it up
into several files based on the class hierarchy. Fortunately, many of these
classes are loosely coupled to each other.

We had a remarkable number of analyzer failures.

I'll fix the bots to analyze across the whole project
in a follow-up patch, that should prevent this
in the future.

@abarth

We'll need this for compositing because we need to switch out the sky.Canvas
when we switch compositing layers.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1218593002.

TBR=abarth

Review URL: https://codereview.chromium.org/1208293002.

New asserts:
- verify that after layout, the size fits the constraints
- verify that after layout, the size isn't infinite
- verify that you don't set the size in performLayout() if you have
  sizedByParent set
- verify that nobody reads your size during layout except you, or your
  parent if they said parentUsesSize:true

Fixes some bugs found by those asserts:
- RenderBlock, RenderStack, and RenderScaffold were not always setting
  parentUsesSize correctly
- RenderScaffold was setting its slot entries to null rather than
  removing them when the slot went away, which led to null derefs in
  certain circumstances

Also, rename a local variable in RenderStack.performLayout() because
it was shadowing a variable on the object itself, which was really
confusing when I first tried to debug this function...

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1213473003.

This also fixes the C++ side to give the right baseline information.
Previously it was giving the baseline distance for the font, but not
for the actual laid-out text.

I considered also providing a "defaultBaseline" accessor that returns
the distance for the actual dominant baseline, but it turns out right
now we never decide the baseline is ideographic. We always use the
alphabetic baseline. We should probably fix that...

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1200233002.

Decouple Canvas from DisplayList and map Picture and PictureRecorder more directly to their Skia counterparts.

Also changes the framework dart code to use the
refactored APIs and fixes the various examples and
tests.

R=abarth@chromium.org, ianh@chromium.org

Review URL: https://codereview.chromium.org/1190123003.

Short-circuit the relayoutSubtreeRoot when the child couldn't change dimensions anyway because the parent constrained it.

The relayout subtree root concept is intended to handle the case where
a node, when it lays itself out for a second time, changes its opinion
about what dimensions it should be. In such a situation, the parent,
if it based its own opinion about what size _it_ should be on the
child's dimensions, would also need to lay itself out again. Thus,
when this scenario is possible, the child remembers the parent, and
when it would be told to relayout, we actually start the layout with
the parent.

In practice, this chains, and we end up with nodes that point to
ancestors ten or more steps up the tree such that when the inner most
child re-lays-out, the whole app ends up relaying out.

This patch tries to short-circuit this for the case where the
constraints being applied to the child are such that actually, the
child has no choice about its dimensions. In that case, the parent
can't change dimensions when the child re-lays-out.

This makes a huge difference on the stocks demo app. Without this, on
the third rendered frame, there are 72 relayoutSubtreeRoot links, the
deepest chain is 8 deep, and 9 of the chains are only 1 level deep.
With it, there are 63 relayoutSubtreeRoot links, the deepest chain is
only 4 deep, and 38 of the chains are only 1 level deep.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1196553004.

Flesh out a README.md file for the SDK.
Make the stocks app test wait for the app to be mounted, to catch some more errors, like typos in the mount callback.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1182053012.

Add a test for RenderDecoratedBox sets up the Paint object correctly.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1185423003.

We can't have two copies of |embedder.dart| or |shell.dart| because they take
ownership of some underlying Mojo handles. Instead of duplicating the code,
this CL makes the old locations just export all the symbols from the new
location. I've also done the same with fetch.dart to avoid code duplication.

Finally, I've removed image_cache.dart in the old location because the only
clients already live in the new world and ought to use the new location.

TBR=ianh@google.com

Review URL: https://codereview.chromium.org/1179923004.

Some files are moved by this:
  Copy framework/node.dart into types/ - preparing for framework/'s decomissioning.
  Move app/scheduler.dart into sky/scheduler.dart - "app" doesn't really make sense.

As part of the SkyBinding cleanup, I made the hit-testing less
RenderBox-specific, by having the HitTestEntry.target member be a
HitTestTarget, which is an interface with the handleEvent() function,
which is then implemented by RenderBox. In theory, someone could now
extend hit testing from the RenderBox world into their own tree of
nodes, and take part in all the same dispatch logic automatically.

This involved moving all the hit testing type definitions into a new
sky/hittest.dart file.

Renamed SkyBinding._app to SkyBinding._instance for clarity.

Moved code around in SkyBinding so that related things are together.

Made WidgetSkyBinding use the existing SkyBinding.instance singleton
logic rather than having its own copy.

I also added some stub README.md files that describe dependencies.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1187393002.

Move app/view.dart to rendering/sky_binding.dart since it's part of the RenderObject API, really (it knows about RenderView intimately).
The tests pass. I didn't check every last example.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1183913006.

Defined constants for all 9 CSS font-weight values
with conventional names from the "Common weight
name mapping" section of
https://developer.mozilla.org/en-US/docs/Web/CSS/font-weight.

The FontWeight enum now just enumerates the actual
CSS weight values.

I've moved the TextStyle class into its own file.

R=ianh@google.com

Review URL: https://codereview.chromium.org/1173323004.

This is a completion of Eric's WIP patch:
https://codereview.chromium.org/1179663005/

Low level support for creating a paragraph that contains
runs of styled text. The styles may be nested.

The Paragraph and RenderParagraph classes have been
replaced by Inline and RenderInline. Styled text is defined
with a tree of InlineText and InlineStyle objects.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1177833012.

Create an example app that demonstrates interactive coordination of an fn tree and a raw RenderObject tree.

Sector changes:
- implement the intrinsic sizing box API on RenderBoxToRenderSectorAdapter
- remove some debug print statements
- fix getIntrinsicDimensions() on RenderSolidColor to return true values
- factor out the default demo

RenderObject changes:
- BoxConstraints.isInfinite() now returns true only if both dimensions are infinite

fn changes:
- implement UINodeToRenderBoxAdapter
- rename RenderObjectToUINodeAdapter to RenderBoxToUINodeAdapter

Tests:
- add a test for sector layout
- make TestRenderView support being run without the unit test framework

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1175423007.

Make old users of RenderSizedBox use RenderConstrainedBox.
Change the semantics of BoxDecoration.apply* to actually apply the provided constraints to the current constraints, rather than the previous behaviour of merging them neutrally.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1189603003.

This CL moves the bulk of the SkyView code out of the |framework| directory
because the |framework| directory was redundant in Dart package import
declarations.

TBR=ianh@google.com

Review URL: https://codereview.chromium.org/1177383006.

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

Review URL: https://codereview.chromium.org/1178293004.

I also removed the leading /, so it is now possible
to use shelldb start sky/sky_home to test.

Also fixed touch_demo.dart and sector layout to
work and not crash.

R=ianh@google.com

Review URL: https://codereview.chromium.org/1177343002.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1178783002.

Separate out the raw (directly manipulating sky.view) examples from the rendering (using RenderObject et al) examples.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1173233002