- always_declare_return_types
- annotate_overrides
- await_only_futures
- omit_local_variable_types
- prefer_collection_literals
- prefer_conditional_assignment
- prefer_final_fields
- prefer_for_elements_to_map_fromiterable
- prefer_if_null_operators
- prefer_spread_collections
- unnecessary_this
- use_function_type_syntax_for_parameters

Bump min SDK to 2.3.0 everywhere to allow using spreads in collection
literals.

Skip an already failing test

Open to feedback on this. Here's how it works at the moment:

There's a new `--coverage` option that you can use to specify the output directory for your coverage. It will create a new output directory if one doesn't already exist.

The tests are run through the engine, and then get spit out to a coverage helper function. That coverage helper function:
**A)** Checks if it's a VM suite
**B)** Gathers coverage if it is
**C)** Outputs coverage to `${suite path}.vm.json`

So, for example, when I run:
```bash
pub run test --coverage hello_world test/vm/simple_repo_test.dart
```

A new file gets added at `hello_world/test/vm/simple_repo_test.dart.vm.json` with the coverage results!

Run analyzer (at a minimum) across all packages at their oldest supported SDK

In one specific test we expect an executable to be able to run the tests
multiple times. For that case we don't want to hard exit ever.

* Refactor test into two packages (#1)

* move test and test_core to packages folder

* rename test_core to test_api

* rename packages to pkgs, add dart.js back to repo

* change pubspec to point to test_api version

* move to correct dir in travis.yml

* Remove duplicate utils.dart

There are still errors in tests which may be harder to fix so we can't
check in the change to analysis options.

This should make it easier to diagnose Dart 2 semantic issues as more of
the places where there can be failures are explicit.

Most of the changes are just adding explicit `as` statements and keeping
the semantics that already existed. In a few places an uninitialized
`var` is given a type, and in others a reused variable name with
different types is split into multiple variables.

The changes in the frontend code are the most risky, since some users
might still be using that code in a non Dart 2 runtime and relying on
looseness which is lost with an explicit cast.

Pin to the dev.60 SDK for now since there are failures on the newer SDK.

- Delete dartium and content shell platforms
- Delete tests related to dartium
- Remove references to these platforms in docs
- Stop installing dartium on Travis

Usage of 1.23 is non-existent
Increase turn-around on Travis

These tests have been flaking all over the place, and with the total
lack of support for content shell coming so soon it doesn't make sense
to spend the resources tracking down and fixing the root cause.

This makes it possible to commit reviewed code to a branch when working
on a larger change that's composed of multiple pull requests.

Runs the following tests:

- dartanalyzer
- dartfmt
- vm tests excluding all browser tags
- dartium tests

Note that the dev SDK appears to leave pub running after a successful run of tests. This will need to be investigated further.