Sort declarations in fix_aggregator.dart

Change-Id: I19c8370fc38fbebc104dca3b6108db10660c5b9f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/145620
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>

pkg/nnbd_migration/lib/src/fix_aggregator.dart

@@ -194,6 +194,17 @@ class FixAggregator extends UnifyingAstVisitor<void> {
   }
 }
 
+/// Reasons that a variable declaration is to be made late.
+enum LateAdditionReason {
+  /// It was inferred that the associated variable declaration is to be made
+  /// late through the late-inferring algorithm.
+  inference,
+
+  /// It was inferred that the associated variable declaration is to be made
+  /// late, because it is a test variable which is assigned during setup.
+  testVariableInference,
+}
+
 /// Base class representing a kind of change that [FixAggregator] might make to
 /// a particular AST node.
 abstract class NodeChange<N extends AstNode> {
@@ -699,17 +710,6 @@ class NodeChangeForTypeAnnotation extends NodeChange<TypeAnnotation> {
   }
 }
 
-/// Reasons that a variable declaration is to be made late.
-enum LateAdditionReason {
-  /// It was inferred that the associated variable declaration is to be made
-  /// late through the late-inferring algorithm.
-  inference,
-
-  /// It was inferred that the associated variable declaration is to be made
-  /// late, because it is a test variable which is assigned during setup.
-  testVariableInference,
-}
-
 /// Implementation of [NodeChange] specialized for operating on
 /// [VariableDeclarationList] nodes.
 class NodeChangeForVariableDeclarationList