fix #27135 and fix #27449 strong mode does not use propagated types

pkg/analyzer/lib/src/generated/resolver.dart

 // Copyright (c) 2014, 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 analyzer.src.generated.resolver;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 6002 matching lines @@
    * If the given [type] is valid, strongly more specific than the
    * existing static type of the given [expression], record it as a propagated
    * type of the given [expression]. Otherwise, reset it to `null`.
    *
    * If [hasOldPropagatedType] is `true` then the existing propagated type
    * should also is checked.
    */
   void recordPropagatedTypeIfBetter(Expression expression, DartType type,
       [bool hasOldPropagatedType = false]) {
     // Ensure that propagated type invalid.
-    if (type == null || type.isDynamic || type.isBottom) {
+    if (strongMode || type == null || type.isDynamic || type.isBottom) {
       if (!hasOldPropagatedType) {
         expression.propagatedType = null;
       }
       return;
     }
     // Ensure that propagated type is more specific than the static type.
     DartType staticType = expression.staticType;
     if (type == staticType || !type.isMoreSpecificThan(staticType)) {
       expression.propagatedType = null;
       return;
@@ skipping 1381 matching lines @@
         !FunctionTypeImpl.relate(
             expectedClosureType,
             staticClosureType,
             (DartType t, DartType s, _, __) =>
                 (t as TypeImpl).isMoreSpecificThan(s),
             new TypeSystemImpl().instantiateToBounds,
             returnRelation: (s, t) => true)) {
       return;
     }
     // set propagated type for the closure
-    closure.propagatedType = expectedClosureType;
+    if (!strongMode) {
+      closure.propagatedType = expectedClosureType;
+    }
     // set inferred types for parameters
     NodeList<FormalParameter> parameters = closure.parameters.parameters;
     List<ParameterElement> expectedParameters = expectedClosureType.parameters;
     for (int i = 0;
         i < parameters.length && i < expectedParameters.length;
         i++) {
       FormalParameter parameter = parameters[i];
       ParameterElement element = parameter.element;
       DartType currentType = _overrideManager.getBestType(element);
       // may be override the type
@@ skipping 3835 matching lines @@
       return null;
     }
     if (identical(node.staticElement, variable)) {
       if (node.inSetterContext()) {
         result = true;
       }
     }
     return null;
   }
 }