Implement type inference for await expressions in front_end.

pkg/analyzer/test/src/task/strong/checker_test.dart

Index: pkg/analyzer/test/src/task/strong/checker_test.dart
diff --git a/pkg/analyzer/test/src/task/strong/checker_test.dart b/pkg/analyzer/test/src/task/strong/checker_test.dart
index c5b45128e256db2d3ffaaa4fc824040e9496ecf8..99c6b46352d2474cc5c974ad632b455ff9f74414 100644
--- a/pkg/analyzer/test/src/task/strong/checker_test.dart
+++ b/pkg/analyzer/test/src/task/strong/checker_test.dart
@@ -922,16 +922,20 @@ dynamic x;
 foo1() async => x;
 Future foo2() async => x;
 Future<int> foo3() async => /*info:DYNAMIC_CAST*/x;
-Future<int> foo4() async => new Future<int>.value(x);
+Future<int> foo4() async => new Future<int>.value(/*info:DYNAMIC_CAST*/x);
 Future<int> foo5() async =>
-    /*error:RETURN_OF_INVALID_TYPE*/new Future<String>.value(x);
+    /*error:RETURN_OF_INVALID_TYPE*/new Future<String>.value(
+        /*info:DYNAMIC_CAST*/x);
 
 bar1() async { return x; }
 Future bar2() async { return x; }
 Future<int> bar3() async { return /*info:DYNAMIC_CAST*/x; }
-Future<int> bar4() async { return new Future<int>.value(x); }
+Future<int> bar4() async {
+  return new Future<int>.value(/*info:DYNAMIC_CAST*/x);
+}
 Future<int> bar5() async {
-  return /*error:RETURN_OF_INVALID_TYPE*/new Future<String>.value(x);
+  return /*error:RETURN_OF_INVALID_TYPE*/new Future<String>.value(
+      /*info:DYNAMIC_CAST*/x);
 }
 
 int y;