* round 2

* deal with null futures

* review

* review

* review

* review

* Add --trace-skia parameter to flutter run

Skia tracing is extremely useful for internal debug, but reduces the
amount of space available in the Dart Timeline buffers.
Disable skia tracing by default and expose them via the --trace-skia
flag.

* Roll Engine to 57a1445a45964d386500c39f5e8d06db060abadb

This adds --preview-dart-2 flag that enables use of Dart 2.0 Frontend in Flutter tools.

This reverts commit 8d07d3f6.

* pass the value of the android sdk

* swap flag

* allow the user to set the android-sdk location

* Include the process' `stdout` and `stderr` when it returns a
  non-zero exit code in `runCheckedAsync()`
* Defensively catch errors in `AndroidDevice.isAppInstalled()`
  and return false

* 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/10203

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

* review

Fixes #10929

Fixes https://github.com/flutter/flutter/issues/10703

This reverts commit b2909a24.

This resubmits the following patches:

1. Use Xcode instruments to list devices (#10801)
Eliminates the dependency on idevice_id from libimobiledevice. Instead,
uses Xcode built-in functionality.

2. Make device discovery asynchronous (#10803)
Migrates DeviceDiscovery.devices and all device-specific lookup to be
asynchronous.

Fixes https://github.com/flutter/flutter/issues/10630

* Revert "Make device discovery asynchronous (#10803)"
This reverts commit 972be9c8.

* Revert "Use Xcode instruments to list devices (#10801)"
This reverts commit 37bb5f13.

This is to resolve a failure that looks related to a bad install of Xcode 8.0
on our build bots and should be reinstated when the infra issue is diagnosed
and resolved.

Instruments worked well when this was originally landed, and on the
following commit, but started failing two commits after this originally
landed. Manual invocation of instruments on the build host currently
results in:

```
dyld: Library not loaded: @rpath/InstrumentsAnalysisCore.framework/Versions/A/InstrumentsAnalysisCore
  Referenced from: /Applications/Xcode8.0.app/Contents/Developer/usr/bin/instruments
  Reason: image not found
Abort trap: 6
```

It appears the /Applications/Xcode8.0.app/Contents/Applications
directory (which contains Instruments) is missing on the host.

Migrates DeviceDiscovery.devices and all device-specific lookup to be
asynchronous.

Eliminates the need for the device/daemon code to get at the iOS/Android
tooling indirectly via Doctor. In tests, we now inject the workflow
objects (or mocks) directly.

* add min version checks for IntelliJ

* validate the installed versions of IntelliJ and the flutter plugin

* review comments

Our emulator detection was based on a simple heuristic that was
failing for the Samsung Galaxy S8. Any heuristic is flawed since
Android devices can report whatever they want to adb, but this
change attempts to tighten the detection by listing known models
(by their ro.hardware property). Again, these values could be
spoofed by emulator system images, but it's less likely to be
an issue than with our previous (and fall-back) heuristic.

Fixes #10203
Related: #10248

For some reaosn, when we discovered our URI, we were re-instantiating
the `Completer` instance variable whose future we listen to in `nextUri()`.
This led to a race between a caller calling `nextUri()` and us discovering
the URI. If we happened to discover our URI before a caller called
`nextUri()`, then they would be left waiting on a future from the newly
allocated `Completer` (which would never complete).

Fixes #10064

Fixes https://github.com/flutter/flutter/issues/9954

Fixes https://github.com/flutter/flutter/issues/9929

Fixes #9866

Add a flutter doctor --android-licenses command that locates and runs the Android SDK license manager (#9892)

See https://github.com/flutter/flutter/issues/8438

Eagerly generate local.properties, and always update the flutter.sdk
setting in it, in case FLUTTER_ROOT has changed.

Fixes #8365.
Fixes #9716 - at least the specific issue reported. My Android Studio
still complains about Gradle versions - it ships with v3.2, but requires
v3.3...

Add a 'generate dependencies' task to the Gradle build, which checks if
the snapshot dependencies file exists, and runs an extra build before
the actual FlutterTask if it doesn't. This makes the first build slower,
but sub-sequent builds (without source changes) much faster.

Fixes #9717.

This message will be picked up by IntelliJ and shown to the user in a toast.

* Let printError print bold as well

* review notes

Note: In a cross-platform context `Uri.path` is not a valid file path. Allways use `fs.path.fromUri` to convert.