Revert "Use native async/await support in pub."

sdk/lib/_internal/pub_generated/lib/src/source/unknown.dart

Index: sdk/lib/_internal/pub_generated/lib/src/source/unknown.dart
diff --git a/sdk/lib/_internal/pub/lib/src/source/unknown.dart b/sdk/lib/_internal/pub_generated/lib/src/source/unknown.dart
similarity index 65%
copy from sdk/lib/_internal/pub/lib/src/source/unknown.dart
copy to sdk/lib/_internal/pub_generated/lib/src/source/unknown.dart
index 714ff5ce33b14ec1c392cdd44270fd90356f6c7f..a3049cb5e05783191f8419ae5f7cf10262ce70f1 100644
--- a/sdk/lib/_internal/pub/lib/src/source/unknown.dart
+++ b/sdk/lib/_internal/pub_generated/lib/src/source/unknown.dart
@@ -22,26 +22,27 @@ class UnknownSource extends Source {
   UnknownSource(this.name);
 
   /// Two unknown sources are the same if their names are the same.
-  bool operator==(other) =>
-      other is UnknownSource &&
-      other.name == name;
+  bool operator ==(other) => other is UnknownSource && other.name == name;
 
   int get hashCode => name.hashCode;
 
-  Future<Pubspec> doDescribe(PackageId id) => throw new UnsupportedError(
-      "Cannot describe a package from unknown source '$name'.");
+  Future<Pubspec> doDescribe(PackageId id) =>
+      throw new UnsupportedError(
+          "Cannot describe a package from unknown source '$name'.");
 
-  Future get(PackageId id, String symlink) => throw new UnsupportedError(
-      "Cannot get an unknown source '$name'.");
+  Future get(PackageId id, String symlink) =>
+      throw new UnsupportedError("Cannot get an unknown source '$name'.");
 
   /// Returns the directory where this package can be found locally.
-  Future<String> getDirectory(PackageId id) => throw new UnsupportedError(
-      "Cannot find a package from an unknown source '$name'.");
+  Future<String> getDirectory(PackageId id) =>
+      throw new UnsupportedError(
+          "Cannot find a package from an unknown source '$name'.");
 
   bool descriptionsEqual(description1, description2) =>
       description1 == description2;
 
   /// Unknown sources do no validation.
   dynamic parseDescription(String containingPath, description,
-                           {bool fromLockFile: false}) => description;
+      {bool fromLockFile: false}) =>
+      description;
 }