Add type inference support for "call" invocations of function expressions.

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

Index: pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
diff --git a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
index 0539e2cb8b59551f33d2de7b89455121b8ca043b..a2f1cb786f49a993e4fdd8ccefcee47da286a3f5 100644
--- a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
@@ -234,9 +234,13 @@ abstract class TypeInferrerImpl extends TypeInferrer {
     } else if (receiverType is DynamicType) {
       return _functionReturningDynamic;
     } else if (receiverType is FunctionType) {
-      // TODO(paulberry): handle the case of invoking .call() or .toString() on
-      // a function type.
-      return _functionReturningDynamic;
+      if (methodName.name == 'call') {
+        return receiverType;
+      } else {
+        // TODO(paulberry): handle the case of invoking .toString() on a
+        // function type.
+        return _functionReturningDynamic;
+      }
     } else if (receiverType is TypeParameterType) {
       // TODO(paulberry): use the bound
       return _functionReturningDynamic;