Add Observatory to sky dart_controller

sky/engine/bindings/builtin.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SKY_ENGINE_BINDINGS_BUILTIN_H_
 #define SKY_ENGINE_BINDINGS_BUILTIN_H_
 
 #include "base/macros.h"
 #include "dart/runtime/include/dart_api.h"
 
 namespace blink {
 
 class Builtin {
  public:
   // Note: Changes to this enum should be accompanied with changes to
   // the builtin_libraries_ array in builtin.cc.
   enum BuiltinLibraryId {
     kBuiltinLibrary,
     kSkyLibrary,
     kMojoInternalLibrary,
+    kIOLibrary,
     kInvalidLibrary,
   };
 
   static void SetNativeResolver(BuiltinLibraryId id);
   static Dart_Handle LoadAndCheckLibrary(BuiltinLibraryId id);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(Builtin);
 };
 
 }  // namespace blink
 
 #endif  // SKY_ENGINE_BINDINGS_BUILTIN_H_