* add a --machine mode to flutter config

* review feedback

* minor tweaks to the output for flutter_tools

* update test expectations

https://github.com/flutter/flutter/issues/10940

* Revert "test missed a mock (#11098)"

This reverts commit 1a01de9a.

* Revert "Roll engine to 9117705b3653565a240314481c63eb93090f7232 (#11114)"

This reverts commit 12b39528.

* Exclude modal barrier from semantics on Android

* Add tests

* Make the drag resistance non-linear

* Let the easing of overscroll have a spring effect too

* Add tests and prevent possible drift by having a slightly smaller resistance when easing the overscroll

* lint

Snapshot dependency files now backslash-escape dependency paths
containing spaces and backslashes.

See: https://codereview.chromium.org/2966903003/

Previously, the snapshot file was recomputed on every build. We now
record checksums for all snapshot inputs (which are catalogued in the
snapshot dependencies file output alongside the snapshot) and only
rebuild if the checksum for any input file (or the previous output file) has
changed.

See https://github.com/flutter/flutter/issues/11051

(Needs https://github.com/dart-lang/sdk/issues/28519)

* AutomaticKeepAlive

A Widget that listens for notifications from widgets that don't want to die.

* Automatically wrap SliverList and SliverGrid children in AutomaticKeepAlive widgets

* Fixes for review comments

Previously, the snapshot file was recomputed on every build. We now
record checksums for all snapshot inputs (which are catalogued in the
snapshot dependencies file output alongside the snapshot) and only
rebuild if the checksum for any input file has changed.

Fixes https://github.com/flutter/flutter/issues/11041

And add a test to verify we don't do this again.

https://github.com/flutter/flutter/issues/10203

* Only one call to createSnapshot exists, and it's in the same library.

* Eliminate conditional logic around the presence of depfilePath, the
  only existing call always passes a non-null depfilePath.

* Output verbose cocoapods output when pod install has an error or if flutter build/run is in -v

* remove repeated stdout

This adds a way to run only a subset of the tests.
(The new flags do the same thing as 'pub run test'.)

* increase the timeout for service discovery

* remove the timeout for discovering service ports

Remove terminating semicolons; they are causing an "code inspection warning" in Android Studio:

```
This inspection reports redundant semicolon (';') token which is not required in Kotlin and may be removed.
```

* Guess sign with the first certificate when multiple are available in machine mode

* review

In the case where the CocoaPods 'pod install' step fails, emit its
stdout to provide any potentially-useful error messages to the user.