This doesn't fully support the JSON reporter yet.

See #50

Users can pass stayAlive: true to keep them open, but this helps ensure
that they won't accidentally have a bunch of isolates hanging around
between tests.

Closes #109

See #109
Closes #93

This is necessary to make configuration work with Google's internal
build system.

This worked with the old expectAsync(), but was broken when the new
functions were introduced. It was causing an analysis error in the
tests.

Small fixes.

This adds `spawnHybridUri()` and `spawnHybridCode()` methods that spawn
VM isolates even when called from the browser. It still needs some
additional work to close the isolates when the test ends by default.

See #109

BUG=
R=nweiz@google.com

Review URL: https://codereview.chromium.org//2557183002 .

Dartium wasn't emitting any standard IO on Windows, which caused us to
stall out waiting for the Observatory URL in debug mode.

See dart-lang/sdk#28034
Closes #425

Closes #503

Review URL: https://codereview.chromium.org//2526223002 .

Fixes #436.

R=nweiz@google.com

Review URL: https://codereview.chromium.org//2515303002 .

I think most of these breakages are due to the 1325b694 merge being
slightly busted.

Add debugging support for the JSON reporter.

Also update the pubspec and changelog.

External tools can use this to communicate with the test runner.

This tracks configuration that makes sense to apply to test suites, as
opposed to Configuration which applies to an entire run and Metadata
which applies to individual tests. This is intended to make it easier
for load separate configurations for separate targets in a live test
runner.

If a web test emitted any kind of message after the browser manager was
closed, the debugging timer would reset and cause the VM not to exit for
an extra three seconds.

Previously, the --precompiled flag only overlayed precompiled JS; all
HTML-file handling was left up to the test package. But the internal
Google infrastructure wants to be able to generate the HTML as well.
This changes the semantics so that both JS and HTML are expected in the
precompiled directory.

Closes #458

Make test iframes visible when debugging.

Closes #429

Closes #485

R=nweiz@google.com
BUG=

Review URL: https://codereview.chromium.org//2392743005 .

This reverts commit 4ca058ce.

Closes #477