- [x] Skip scanning the file system if we already have the Dart dependency set.
Fixes#9376
```
Performing hot reload...
Reloaded 1 of 418 libraries in 888ms.
Performing hot reload...
Reloaded 1 of 418 libraries in 871ms.
** UNTAR dragontail under project root **
Performing hot reload...
Reloaded 0 of 418 libraries in 443ms.
** UNTAR dragontail under lib/ **
Performing hot reload...
Reloaded 0 of 418 libraries in 385ms.
```
* Roll Dart to 1.23.0-dev.11.3.
This is expected to fix the Windows crashes reported in https://github.com/flutter/flutter/issues/8912.
* fix tests
* Roll to 1.23.0-dev.11.5
* Fix tests
The old `whichAll` implementation was not considering different extensions for executables on Windows. By defering to OS-built-in tools we avoid implementing it.
Fixes#8882.
* Make ProcessSignals portable
This removes the need to wrap unsupported signals with in `if (!platform.isWindows) ..`.
It also allows us to implement a work around for breaking the Windows console when flutter is exited with Ctrl+C.
* review comments
* adding tests
* add license header
1. Add `PortScanner` abstraction so that we don't do actual port scanning
in tests.
2. Don't change the real `cwd` of the isolate during tests, as it affects
all tests, not just the current running test.
Fixes#8761
It was resulting in weird situations where the tool would dump an
error message and stack but not quit, or would fail hard but then just
hang.
Instead, specifically catch errors you expect. As an example of this,
there's one error we expect from the DartDependencySetBuilder, so we
catch that one, turn it into a dedicated exception class, then in the
caller catch that specific exception.
This implements the `DartDependencySetBuilder` completely in Dart instead of calling out to `sky_snapshot` (Linux/Mac) or `gen_snapshot` (Windows) and allows us to use the same code path on all supported host platforms.
It also slightly reduces hot reload times on Linux from ~750ms to ~690ms for the unchanged flutter_gallery app and significantly reduces hot reload times on Windows from almost 1.5s to just slightly slower than on Linux.
This change will also allow us to retire `sky_snapshot` completely in the future.
1. Add matchers for the `ProcessExit` exception class
2. Add ability to control the setup of the `AppContext` we use in
`testUsingContext()`
3. Clean up the code that figures out the location of `Cache.flutterRoot`
such that it works with `pub run test`. It previously only worked
when the tests were invoked with standalone `dart`
`#3` above will also help unblock #7941
