Split dart_api.h into multiple parts:

runtime/vm/custom_isolate_test.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
+#include "include/dart_native_api.h"
 
 #include "vm/unit_test.h"
 
 // Custom Isolate Test.
 //
 // This mid-size test uses the Dart Embedding Api to create a custom
 // isolate abstraction.  Instead of having a dedicated thread for each
 // isolate, as is the case normally, this implementation shares a
 // single thread among the isolates using an event queue.
 
@@ skipping 317 matching lines @@
     event = event_queue->Get();
   }
   OS::Print("-- Finished event loop --\n");
   EXPECT_STREQ("Received: 43", saved_echo);
   free(const_cast<char*>(saved_echo));
 
   delete event_queue;
 }
 
 }  // namespace dart