Infer the return types of local functions where appropriate.

pkg/front_end/testcases/inference/infer_local_function_referenced_before_declaration.dart.strong.expect

+library test;
+import self as self;
+import "dart:core" as core;
+
+const field dynamic #errors = const <dynamic>["pkg/front_end/testcases/inference/infer_local_function_referenced_before_declaration.dart:9:74: Error: Previous use of 'g'.\n  /*@returnType=dynamic*/ f() => /*error:REFERENCED_BEFORE_DECLARATION*/ g();\n                                                                         ^"]/* from null */;
+static method test() → dynamic {
+  function f() → dynamic
+    return throw new core::NoSuchMethodError::_withType(null, #g, 32, <dynamic>[].toList(growable: false), <dynamic, dynamic>{}, null);
+  const core::_ConstantExpressionError::•()._throw(new core::_CompileTimeError::•("pkg/front_end/testcases/inference/infer_local_function_referenced_before_declaration.dart:14:3: Error: Can't declare 'g' because it was already used in this scope.\n  g() => 0;\n  ^"));
+  () → dynamic v = f;
+}
+static method main() → dynamic {}