Add support for converted closures with explicit contexts to VM

pkg/kernel/lib/transformations/closure/info.dart

 // 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.
 
 library kernel.transformations.closure.info;
 
 import '../../ast.dart'
     show
         Class,
         Constructor,
@@ skipping 75 matching lines @@
     ///       }
     ///     }
     ///
     /// Here the parameter shouldn't be captured into a context in the
     /// initializer.  However, [currentFunction] is `null` if not set, and
     /// `function[node.variable]` in this case points to the [FunctionNode] of
     /// the constructor (which is not `null`).  It leads to `x` being treated as
     /// captured, because it's seen as used outside of the function where it is
     /// declared.  In turn, it leads to unnecessary context creation and usage.
     ///
-    /// We also need to visit the parameters to the function node before the
-    /// initializer list. Since the default [visitChildren] method of
-    /// [Constructor] will visit initializers first, we manually visit the
-    /// parameters here.
-    ///
-    /// TODO(sjindel): Don't visit the parameters twice.
-    ///
+    /// Another consideration is the order of visiting children of the
+    /// constructor: [node.function] should be visited before
+    /// [node.initializers], because [node.function] contains declarations of
+    /// the parameters that may be used in the initializers.  If the nodes are
+    /// visited in another order, the encountered parameters in initializers
+    /// are treated as captured, because they are not yet associated with the
+    /// function.
     beginMember(node, node.function);
     saveCurrentFunction(() {
       currentFunction = currentMemberFunction;
-      visitList(node.function.positionalParameters, this);
-      visitList(node.function.namedParameters, this);
-      super.visitConstructor(node);
+
+      visitList(node.annotations, this);
+      node.name?.accept(this);
+      node.function?.accept(this);
+      visitList(node.initializers, this);
     });
     endMember();
   }
 
   visitProcedure(Procedure node) {
     beginMember(node, node.function);
     super.visitProcedure(node);
     endMember();
   }
 
@@ skipping 85 matching lines @@
 
   saveCurrentFunction(void f()) {
     var saved = currentFunction;
     try {
       f();
     } finally {
       currentFunction = saved;
     }
   }
 }