Sort imports for dartfmt

[DartBot]

This issue was originally filed by [email protected]

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What steps will clearly show the issue / need for enhancement?

1. Run dartfmt -t on attached foo.dart
2. Observe that imports are not in order.

What is the current output?
`
import 'package:a_star/a_star_2d.dart';
import 'package:zx/zx.dart';
import 'dart:convert';
import 'dart:async';
import 'package:a_star/a_star.dart';

void main() {
}
`

What would you like to see instead?
`
import 'dart:convert';
import 'dart:async';
import 'package:a_star/a_star.dart';
import 'package:a_star/a_star_2d.dart';
import 'package:zx/zx.dart';

void main() {
}
`

What version of the product are you using? On what operating system?
Dart VM version: 1.5.3 (Thu Jul 3 02:27:23 2014) on "macos_x64"

Please provide any additional information below.

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Attachment:
foo.dart (166 Bytes)

[DartBot]

This comment was originally written by [email protected]

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Correction on "What would you like to see":
`
import 'dart:async';
import 'dart:convert';
import 'package:a_star/a_star.dart';
import 'package:a_star/a_star_2d.dart';
import 'package:zx/zx.dart';

void main() {
}
`

[iposva-google]

Added Area-Formatter, Triaged labels.

[munificent]

Phil, this is a linter bug. Want to do something with it?

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Set owner to @pq.
Removed Area-Formatter label.
Added Area-Analyzer label.

[pq]

Indeed, yes. Thanks Bob.

Moved here: #57172

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Added MovedToGithub label.