Fix for resynthesizing FutureOr in not strong mode.

R=brianwilkerson@google.com, paulberry@google.com

Bug:
Change-Id: I239bb013cb04c6e1ab07d644e3cca16119885321
Reviewed-on: https://dart-review.googlesource.com/6743
Reviewed-by: Paul Berry <paulberry@google.com>

pkg/analyzer/lib/src/kernel/resynthesize.dart

@@ -41,6 +41,11 @@ class KernelResynthesizer implements ElementResynthesizer {
    */
   DartType get typeType => getLibrary('dart:core').getType('Type').type;
 
+  /**
+   * Return `true` if strong mode analysis should be used.
+   */
+  bool get strongMode => _analysisContext.analysisOptions.strongMode;
+
   @override
   Element getElement(ElementLocation location) {
     List<String> components = location.components;
@@ -810,8 +815,13 @@ class _KernelUnitResynthesizerContextImpl
     if (kernelType is kernel.VoidType) return VoidTypeImpl.instance;
 
     if (kernelType is kernel.InterfaceType) {
-      return _getInterfaceType(context, kernelType.className.canonicalName,
-          kernelType.typeArguments);
+      var name = kernelType.className.canonicalName;
+      if (!libraryContext.resynthesizer.strongMode &&
+          name.name == 'FutureOr' &&
+          name.parent.name == 'dart:async') {
+        return DynamicTypeImpl.instance;
+      }
+      return _getInterfaceType(context, name, kernelType.typeArguments);
     }
 
     if (kernelType is kernel.TypeParameterType) {

pkg/analyzer/test/generated/non_error_resolver_kernel_test.dart

@@ -18,18 +18,6 @@ class NonErrorResolverTest_Kernel extends NonErrorResolverTest_Driver {
   @override
   bool get enableKernelDriver => true;
 
-  @override
-  @failingTest
-  test_async_flattened() async {
-    return super.test_async_flattened();
-  }
-
-  @override
-  @failingTest
-  test_async_future_int_with_return_future_int() async {
-    return super.test_async_future_int_with_return_future_int();
-  }
-
   @override
   @failingTest
   test_commentReference_beforeMethod() async {

pkg/analyzer/test/src/summary/resynthesize_kernel_test.dart

@@ -9,6 +9,7 @@ import 'dart:async';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/dart/element/element.dart';
+import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/kernel/resynthesize.dart';
 import 'package:front_end/byte_store.dart';
@@ -117,6 +118,10 @@ class ResynthesizeKernelStrongTest extends ResynthesizeTest {
     return resynthesizer.getLibrary(testUriStr);
   }
 
+  @override
+  AnalysisOptionsImpl createOptions() =>
+      super.createOptions()..strongMode = true;
+
   @failingTest
   @fastaProblem
   test_class_constructor_field_formal_multiple_matching_fields() async {