Revert "Add unawaited to package:meta"

This reverts commit 0d44449.

Reason for revert: Breaks Flutter HHH and the Dart->Flutter roll.

Original change's description:
> Add unawaited to package:meta
> 
> Change-Id: I09df4989591327bd4d148e73a5887b900902576c
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/152680
> Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
> Reviewed-by: Jake Macdonald <jakemac@google.com>

TBR=brianwilkerson@google.com,jakemac@google.com

Change-Id: I71f491bccc37508a24b7f6f9d051ed914bafeccd
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153351
Reviewed-by: Tess Strickland <sstrickl@google.com>
Commit-Queue: Tess Strickland <sstrickl@google.com>

DEPS

@@ -123,7 +123,7 @@ vars = {
   "oauth2_tag": "1.6.0",
   "package_config_rev": "9c586d04bd26fef01215fd10e7ab96a3050cfa64",
   "path_rev": "4f3bb71843fe5493ba490828a1721821d7b33746",
-  "pedantic_tag": "v1.9.1",
+  "pedantic_tag": "v1.9.0",
   "ply_rev": "604b32590ffad5cbb82e4afef1d305512d06ae93",
   "pool_rev": "86fbb2cde9bbc66c8d159909d2f65a5981ea5b50",
   "protobuf_rev": "3746c8fd3f2b0147623a8e3db89c3ff4330de760",

pkg/meta/CHANGELOG.md

@@ -1,20 +1,9 @@
-## 1.3.0-nnbd
+## 1.2.0-nnbd
 
 * Opt into null safety.
-
-## 1.2.1
-
-* Fixed a bug by adding an import of dart:async so that the code really is
-  compatible with the lower bound of the SDK constraints.
-
-## 1.2.0
-
 * Introduce `@doNotStore` to annotate methods, getters and functions to
   indicate that values obtained by invoking them should not be stored in a
   field or top-level variable.
-* Introduce `unawaited` to mark invocations that return a `Future` where it's
-  intentional that the future is not being awaited. (Moved from
-  `package:pedantic`.)
 
 ## 1.1.8
 

pkg/meta/lib/meta.dart

@@ -1,9 +1,8 @@
-// Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// Constants and functions that developers can use to express the intentions
-/// that otherwise can't be deduced by statically analyzing the source code.
+/// Constants for use in metadata annotations.
 ///
 /// See also `@deprecated` and `@override` in the `dart:core` library.
 ///
@@ -13,7 +12,7 @@
 /// function's name differently.
 ///
 /// For information on installing and importing this library, see the [meta
-/// package on pub.dev](https://pub.dev/packages/meta). For examples of using
+/// package on pub.dev](https://pub.dev/packages/meta).  For examples of using
 /// annotations, see
 /// [Metadata](https://dart.dev/guides/language/language-tour#metadata) in the
 /// language tour.
@@ -267,26 +266,6 @@ const _VisibleForOverriding visibleForOverriding = _VisibleForOverriding();
 ///   library which is in the `test` folder of the defining package.
 const _VisibleForTesting visibleForTesting = _VisibleForTesting();
 
-/// Indicates to tools that [future] is intentionally not `await`-ed.
-///
-/// In an `async` context, it is normally expected that all [Future]s are
-/// awaited, and that is the basis of the lint `unawaited_futures`. However,
-/// there are times where one or more futures are intentionally not awaited.
-/// This function may be used to ignore a particular future. It silences the
-/// `unawaited_futures` lint.
-///
-/// ```
-/// Future<void> saveUserPreferences() async {
-///   await _writePreferences();
-///
-///   // While 'log' returns a Future, the consumer of 'saveUserPreferences'
-///   // is unlikely to want to wait for that future to complete; they only
-///   // care about the preferences being written).
-///   unawaited(log('Preferences saved!'));
-/// }
-/// ```
-void unawaited(Future<void>? future) {}
-
 /// Used to annotate a class.
 ///
 /// See [immutable] for more details.

pkg/meta/pubspec.yaml

@@ -1,11 +1,11 @@
 name: meta
-version: 1.3.0-nnbd
+version: 1.2.0-nnbd
+author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/sdk/tree/master/pkg/meta
 description: >
- This library contains the declarations of constants and functions that
- developers can use to express the intentions that otherwise can't be deduced by
- statically analyzing the source code. These declarations are intended to be
- used by tools to provide a better user experience.
+ This library contains the definitions of annotations that provide additional
+ semantic information about the program being annotated. These annotations are
+ intended to be used by tools to provide a better user experience.
 environment:
   # This must remain a tight constraint (only allow dev versions) until nnbd is
   # stable.