* Fix packages tests when run off bots

* Tweak dependencies to make bots happy

* Review comment

https://github.com/flutter/flutter/issues/14519

https://github.com/flutter/flutter/issues/14798

Fixes https://github.com/flutter/flutter/issues/14751

* Fix snapshot fingerprint check for --preview-dart-2.

* Remove printTraces

These URLs all automatically redirect HTTP to HTTPS so makes sense to point users at the secure versions.

This will allow other tools to call into the roll_dev script
to know what version is about to be published without actually
publishing.

https://github.com/flutter/flutter/issues/14751

* fix potential call on null

* review

This is needed to support running with local engine's dart sdk.

This is follow-up to https://github.com/flutter/flutter/pull/14702.

* All lists produced by JSON parsing are List<dynamic>. If more
speficic type is required then they need to be explicitly cast, e.g.
using castFrom helper;
* Function of type (ByText) -> Finder is not a subtype of
(SerializableFinder) -> Finder because ByText is in the contravariant
position;
* In Dart 2 typed(any) should be used instead of any in mockito based
tests.

* Added sample code to AnimatedOpacity docs

Merging on red tree to get back to green.

- Remove redundant strong flag as it is the default for preview-dart-2
now

* Created plumbing but has stream problem

* testing with makePipe

* Trying pipe but not really getting anywhere

* works by repeatedly reading line

* Minor cleanup

* works

* Clean up pipe after use.

* Move the last status forward

* Make sure failed script commands bubble up

* Small glow overscroll dartdoc addition

* Directly specify [MaterialApp]

* review

This reverts commit b3e4976c.

Reports from that commit included:

* Doctor hanging
* Doctor prompting to install JDK
* AnsiStatus.cancel() printing elapsed time and extra newline
* Printing extra spinner character at the end of each line

up the latest Dart roll

- Resubmit https://github.com/flutter/flutter/pull/14392 to fix
compilation errors