Updates `test` to be constraint-compatible with the latest analyzer (0.28.0-alpha.1).

BUG=
R=brianwilkerson@google.com, nweiz@google.com

Review URL: https://codereview.chromium.org//2255083003 .

R=jakemac@google.com

Review URL: https://codereview.chromium.org//2232533002 .

Closes #327

R=leafp@google.com

Review URL: https://codereview.chromium.org//2184543002 .

BUG=https://github.com/dart-lang/test/issues/442
R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2124983005 .

Closes #393

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2099553002 .

Closes #394

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2123353002 .

This moves the responsibility for printing skip messages to the engine,
rather than the reporter. Reporters now just need to choose how to
display the messages produced by the engine.

This lays the groundwork for #394, since skip messages can now be
emitted during the run of a test.

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2091173002 .

This makes it possible for a test to be marked skip based on its runtime
behavior rather than being strictly based on its metadata.

See #393 and #394

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2099503002 .

Hide strong-mode warnings in test directory
Remove unused imports and fields
Consolidate line splitter instances

R=nweiz@google.com

Review URL: https://codereview.chromium.org//2068363002 .

The new constraint reflects the actual APIs we're using.

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2087003004 .

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2086743002 .

Closes #420

Review URL: https://codereview.chromium.org//2066113002 .

This version hasn't been released yet.

R=jakemac@google.com, kevmoo@google.com

Review URL: https://codereview.chromium.org//2048773002 .

This output was added in a recent dart2js version, and it's redundant
with test's own output. It's also breaking tests.

R=jakemac@google.com, kevmoo@google.com

Review URL: https://codereview.chromium.org//2044263002 .

R=cbracken@google.com

Review URL: https://codereview.chromium.org//2042403003 .

This is useful internally for Google, and is not considered a public
feature with stability guarantees.

Currently this doesn't support --pub-serve mode. If that becomes
necessary, it can be added later.

R=cbracken@google.com

Review URL: https://codereview.chromium.org//2040883003 .

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2039413002 .

These are only intended to be used by Google's internal test runner.
Their API is not public nor is it guaranteed to be stable. They're being
moved into the external repository to ease the pain of merging.

R=cbracken@google.com

Review URL: https://codereview.chromium.org//2009163003 .

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2012113002 .

This prepares for https://codereview.chromium.org/1994743003/, which
moves some of these functions into the collection package. Once that
lands, we'll add a follow-up CL to use those APIs from collection.

R=jakemac@google.com

Review URL: https://codereview.chromium.org//1991303002 .

R=jmesserly@google.com

Review URL: https://codereview.chromium.org//1993023002 .

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1993453002 .

We weren't notifying the controller when all the live tests had been
added to the suite.

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1981283006 .

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1984143003 .

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1960503002 .

Internal users want to use this.

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1887853002 .

Closes #427

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1950673002 .

R=rnystrom@google.com, jmesserly@google.com

Review URL: https://codereview.chromium.org//1921913004 .

Closes #421

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1890853003 .

We were closing hidden tests in Engine.close(), but this isn't
necessary. A test is only hidden if it's complete, complete tests
don't block closing their parent suites, *and* closing the parent suite
will close the test anyway.

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1879823002 .

Looks like we hadn't run the analyzer against all the top-level
libraries.

We no longer generate a file called runInIsolate.dart, so there's no
reason to fold it out of our stack chains.

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1860843002 .

R=kevmoo@google.com

Review URL: https://codereview.chromium.org//1859863002 .

Fix _wrapArgs.

See dart-lang/matcher@400e87928fdceeee883c95c8a81e96fdacfdc399

Update README links to configuration documentation