This enables using GoldensClient from the flutter driver file for the
embedded Android views test.

flutter_goldens.dart has a transitive dependency on dart:ui so it cannot
be included in non Flutter apps. Splitting it out allows us to use it
from driver tests.

This also removes the visibleForTesting annotation from GoldensClient.

This reverts commit 7a9dd709.

Bug: https://github.com/flutter/flutter/issues/19490

* Drawer fix

* fixed nits

* fixed nits

* fixed nits

* final change

* Drawer fix final

* Skip tests instead of expecting failure, because expected failure = timeout which is slow

Some of these tests are known to fail and were coded to expect it; however because the failure is a timeout it's just dragging out test runs (shortening timeouts will make the tests flakier).

* Make it easier to find skipped tests

* Change SKIP to TODO

I switched to just checking for spaces and tabs, since otherwise it expresses a preference for line endings that I think should be taken care of at the git level (and I think they are).

I also fixed a bug where I was looking for ".yml" instead of "*.yml" files, and clarified an output message.

remove the option to pass in the --no-preview-dart-2 flag to analysis

Enables animated curve diagrams in the documentation, replacing the static images.

Fixes #19617

I changed the wording that it was depending on in my last commit. Oops.

Disallow calling stop() or cancel() multiple times. This means that
when you use startProgress you have to more carefully think about what
exactly is going on.

Properly cancel startProgress in non-ANSI situations, so that
back-to-back startProgress calls all render to the console.

This was added for https://github.com/lemurheavy/coveralls-public/issues/1103 but that didn't help.

This reverts commit c36032c6, because
we're missing some credentials for pushing the gallery.

Submitting TBR to unbreak the build.

TBR=tvolkert

This moves the docs generation and gallery upload to Cirrus CI, which is another step in turning off
Travis.

Fixes #19523