Tabs should only scroll on a horizontal TabBarView fling

Workaround to re-enable test

This is a workaround for:
   https://github.com/dart-lang/sdk/issues/25246

Use a newer version of dartdoc

Custom layouts use shouldRelayout() delegate methods instead of tokens

CustomMultiChildLayout and CustomOneChildLayout now use their delegate's shouldRelayout() method instead of a "token" to decide if layout is needed.

MultiChildLayoutDelegate and OnChildLayoutDelegate are now expected to be stateless, i.e. they'll typically be built each time their custom layout widget is built. If the identical layout delegate is provided to a new custom layout, layout will not happen.

Revised the bottom sheet implementation per the new custom layout classes. Removed a SizeObserver.

Fixes #899

CustomMultiChildLayout and CustomOneChildLayout now use their delegate's shouldRelayout() method instead of a "token" to decide if layout is needed.

MultiChildLayoutDelegate and OnChildLayoutDelegate are now expected to be stateless, i.e. they'll typically be built each time their custom layout widget is built. If the identical layout delegate is provided to a new custom layout, layout will not happen.

Revised the bottom sheet implementation per the new custom layout classes. Removed a SizeObserver.

Fixes #899

remove todos for service extension params

Export dependent class from newton package

expose flutter debug functionality using VM service extensions

Update test.sh

Add the -q (quiet) flag to gsutil uploads.

Update test.sh

gen dartdoc using the flutter styles

Switch docs to docs.flutter.io

That site is now live.

See if fixing indent fixes our missing caching

@abarth

rev engine

Fix formatting issue

Add nicer logging/reporting to dev/update_packages.dart

Makes it more obvious where we are spending our time on Travis.

Also added travis caching for the global pub cache to
speed this up!  Modeled what dartdoc does:
https://github.com/dart-lang/dartdoc/blob/master/.travis.yml#L13

@Hixie

Rename stocks/tests to stocks/test

This matches the naming pattern expected from package:test
`flutter test` doesn't care, since it finds all _test.dart
files and runs them regardless of directory.

@Hixie

Fix build breakage

Split out Instrumentation logic from WidgetTester

This will allow writing tests/benchmark which want to use
the engine's default beginFrame and normal passage of time.

@Hixie

Always import our packages when analyzing.

Only set tolerance if simulation is non-null

Fixes #898

Update SoundEffectPlayer to use the SoundPool API