fix #620, infer the input files from sources

test/codegen_expected/language/inline_super_test.js

-//FAILED TO COMPILE
+dart_library.library('language/inline_super_test', null, /* Imports */[
+  'dart_sdk',
+  'expect'
+], function load__inline_super_test(exports, dart_sdk, expect) {
+  'use strict';
+  const core = dart_sdk.core;
+  const dart = dart_sdk.dart;
+  const dartx = dart_sdk.dartx;
+  const expect$ = expect.expect;
+  const inline_super_test = Object.create(null);
+  let VoidTodynamic = () => (VoidTodynamic = dart.constFn(dart.definiteFunctionType(dart.dynamic, [])))();
+  inline_super_test.Percept = class Percept extends core.Object {};
+  inline_super_test.Actor = class Actor extends core.Object {
+    new(percept) {
+      this.percept = percept;
+    }
+  };
+  dart.setSignature(inline_super_test.Actor, {
+    constructors: () => ({new: dart.definiteFunctionType(inline_super_test.Actor, [dart.dynamic])})
+  });
+  inline_super_test.LivingActor = class LivingActor extends inline_super_test.Actor {
+    new() {
+      super.new(new inline_super_test.Percept());
+    }
+  };
+  dart.setSignature(inline_super_test.LivingActor, {
+    constructors: () => ({new: dart.definiteFunctionType(inline_super_test.LivingActor, [])})
+  });
+  inline_super_test.main = function() {
+    expect$.Expect.isTrue(inline_super_test.Percept.is(new inline_super_test.Player().percept));
+  };
+  dart.fn(inline_super_test.main, VoidTodynamic());
+  inline_super_test.Player = class Player extends inline_super_test.LivingActor {
+    new() {
+      super.new();
+    }
+  };
+  dart.setSignature(inline_super_test.Player, {
+    constructors: () => ({new: dart.definiteFunctionType(inline_super_test.Player, [])})
+  });
+  // Exports:
+  exports.inline_super_test = inline_super_test;
+});