Adding hooks for new reporters and test platforms. These hooks are not intended to be a part of the external API and thus are aptly documented.

* plumb chain-stack-traces configuration through

* correctly plumb new flag through and add corresponding tests

* add example command

* chains -> chained

Dartfmt *.dart

* correctly kill Dartium on Linux

* adding try catch

* fix style

It’s not needed at runtime.
Allows us to keep pkg/js as a dev dependency and keep DDC happy

Fixes https://github.com/dart-lang/test/issues/567

Hoping to get the bots to a semi-sane spot

BUG=
R=kevmoo@google.com

Review-Url: https://codereview.chromium.org//2745253004 .

Closes #555

BUG=
R=nweiz@google.com

Review-Url: https://codereview.chromium.org//2740003005 .

Closes #554

We're using a feature that was introduced in
1.6.0 (Disconnector.disconnect's return value).

Closes #556

This brings in changes from dart-lang/oss_project_templates#10 and adds
some extra test-specific information.

Closes #535

Closes #539

If the StreamChannel returned by PlatformPlugin.loadChannel() emits an
error through sink.close(), that error is now properly treated as an
error in the load suite for that channel.

Closes #542

This prints debugging information only if the test actually fails.

Fixes error when running with pub.

Failed to precompile test:test:
'package:test/src/frontend/throws_matcher.dart': error: line 17 pos 41: unexpected token ';'

This also adds a (private) AsyncMatcher class that makes it easier to
define asynchronous matchers, and generally improves the formatting of
those matchers.

This reverts commit 35f9d92a.

dart-lang/vm_service_client#13 has now landed.

This doesn't fully support the JSON reporter yet.

See #50