Bindings now have a debugRegisterServiceExtensions() method that is
invoked in debug mode (only). (Once we have a profile mode, there'll be
a registerProfileServiceExtensions() method that gets called in that
mode only to register extensions that apply then.)

The BindingBase class provides convenience methods for registering
service extensions that do the equivalent of:

```dart
void extension() { ... }
bool extension([bool enabled]) { ... }
double extension([double extension])  { ... }
Map<String, String> extension([Map<String, String> parameters]) { ... }
```

The BindingBase class also itself registers ext.flutter.reassemble,
which it has call a function on the binding called
reassembleApplication().

The Scheduler binding now exposes the preexisting
ext.flutter.timeDilation.

The Renderer binding now exposes the preexisting ext.flutter.debugPaint.

The Renderer binding hooks reassembleApplication to trigger the
rendering tree to be reprocessed (in particular, to fix up the
optimisation closures).

All the logic from rendering/debug.dart about service extensions is
replaced by the above.

I moved basic_types to foundation.

The FlutterWidgets binding hooks reassembleApplication to trigger the
widget tree to be entirely rebuilt.

Flutter Driver now uses ext.flutter.driver instead of
ext.flutter_driver, and is hooked using the same binding mechanism.
Eventually we'll probably move the logic into the Flutter library so
that you just get it without having to invoke a special method first.

To be more consistent with other parts of the platform:

* put the binding in a binding.dart file.

* rearrange some members of the Scheduler class to be more close to
  execution order.

* factor out Priority class into its own file.

* add more dart docs.

* [driver] "waitFor" command in place of broken "exits"

* [driver] wait using frame callback

* rename the --develop option to --debug

* fail if both --debug and --deploy are specified

add explicit paths to the flutter recipies

Analyze CLI option to specify a custom Dart SDK.

Handy for testing against specific local SDK builds.

(Note that the option is hidden.)

* download android-arm-deploy

* wire up --deploy to android-arm-deploy

* fix interpolation

* use the new cache code to locate more artifacts

* add todo

* review comments

* find all repo packages

* .dartignore

+ Add new demo to gallery to show data tables. (This currently doesn't
use a Card; I'll create a Card version in a subsequent patch.)

+ Fix checkbox alignment. It now centers in its box regardless.

+ Add Colors.black54.

+ Some minor fixes to dartdocs.

+ DataTable, DataColumn, DataRow, DataCell

+ RowInkWell

+ Augment dartdocs of materia/debug.dart.

+ DropDownButtonHideUnderline to hide the underline in a drop-down when
  used in a DataTable.

+ Add new capabilities to InkResponse to support RowInkWell.

+ Augment dartdocs of materia/material.dart.

+ Add an assert to catch nested Blocks.

+ Fix a crash in RenderBox when you remove an object and an ancestor
  used its baseline. (https://github.com/flutter/flutter/issues/2874)

+ Fix (and redocument) RenderBaseline/Baseline.

+ Add flex support to IntrinsicColumnWidth.

+ Document more stuff on the RenderTable side.

+ Fix a bug with parentData handling on RenderTable children.

+ Completely rewrite the column width computations. The old logic made
  no sense at all.

+ Add dartdocs to widgets/debug.dart.

+ Add a toString for TableRow.

Fixes https://github.com/flutter/flutter/issues/3363

Fixes https://github.com/flutter/flutter/issues/3352

If two repaint boundaries mark themselves dirty, but the second one is a
child of the first, then the second one will get repainted by the first
and then when we come to paint it directly, we get confused because it
isn't dirty any more.

We ran into this in layout before. Apply the same fix. Also, apply the
same fix to composition while we're at it.

Add a Performance Overlay toggle to the Gallery app

Exception stack variable was shadowing the function argument stack.

We're getting back to the point where we have a bunch of foundation APIs
and it's getting confusing having them mixed with services/.

Make update-packages cover dev/benchmarks.

update-packages only looks one level down, instead of
changing that, I'm just adding dev/benchmarks explicitly.

This will unbreak the bots which are dying trying to
flutter drive dev/benchmarks/complex_layout without
pub get having been run there.

@yjbanov @devoncarew

...even if the test fails.

until we have a fix for the breaking changes

Adding `@optionalTypeArgs`.

With the new dev build we've got the updated linter and so can use the `@optionalTypeArgs` annotation (in `meta 0.12.0`).

Bonus: this lets us clean up one more Regexp in the `analyze` command! :)

Add a basic scrolling test for the Gallery home page.