Allow the VM to read Kernel files with external libraries

runtime/vm/kernel_reader.cc

 // Copyright (c) 2016, 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 "vm/kernel_reader.h"
 
 #include <string.h>
 
 #include "vm/dart_api_impl.h"
 #include "vm/kernel_binary.h"
@@ skipping 235 matching lines @@
       }
     }
   }
 }
 
 void KernelReader::ReadLibrary(intptr_t kernel_offset) {
   builder_.SetOffset(kernel_offset);
   LibraryHelper library_helper(&builder_);
   library_helper.ReadUntilIncluding(LibraryHelper::kCanonicalName);
   Library& library = LookupLibrary(library_helper.canonical_name_);
+  // The Kernel library is external implies that it is already loaded.
+  ASSERT(!library_helper.IsExternal() || library.Loaded());
   if (library.Loaded()) return;
 
   library_helper.ReadUntilIncluding(LibraryHelper::kName);
   library.SetName(H.DartSymbol(library_helper.name_index_));
 
   // The bootstrapper will take care of creating the native wrapper classes, but
   // we will add the synthetic constructors to them here.
   if (library.name() ==
       Symbols::Symbol(Symbols::kDartNativeWrappersLibNameId).raw()) {
     ASSERT(library.LoadInProgress());
@@ skipping 737 matching lines @@
   initializer_fun.set_result_type(AbstractType::Handle(zone, field.type()));
   initializer_fun.set_is_debuggable(false);
   initializer_fun.set_is_reflectable(false);
   initializer_fun.set_is_inlinable(false);
   return new (zone) ParsedFunction(thread, initializer_fun);
 }
 
 }  // namespace kernel
 }  // namespace dart
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)