Do not set root library to null while creating the snapshot, just use whatever is there, it is set …

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, 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_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
 #include "vm/class_finalizer.h"
@@ skipping 1358 matching lines @@
   Dart_Handle state = Api::CheckAndFinalizePendingClasses(T);
   if (::Dart_IsError(state)) {
     return state;
   }
   I->heap()->CollectAllGarbage();
 #if defined(DEBUG)
   FunctionVisitor check_canonical(T);
   I->heap()->IterateObjects(&check_canonical);
 #endif  // #if defined(DEBUG).
 
-  // Since this is only a snapshot the root library should not be set.
-  I->object_store()->set_root_library(Library::Handle(Z));
   FullSnapshotWriter writer(vm_isolate_snapshot_buffer,
                             isolate_snapshot_buffer,
                             NULL, /* instructions_snapshot_buffer */
                             ApiReallocate,
                             false, /* snapshot_code */
                             true /* vm_isolate_is_symbolic */);
   writer.WriteFullSnapshot();
   *vm_isolate_snapshot_size = writer.VmIsolateSnapshotSize();
   *isolate_snapshot_size = writer.IsolateSnapshotSize();
   return Api::Success();
@@ skipping 4578 matching lines @@
   return Api::Success();
 }
 #endif  // DART_PRECOMPILED_RUNTIME
 
 
 DART_EXPORT bool Dart_IsRunningPrecompiledCode() {
   return Dart::IsRunningPrecompiledCode();
 }
 
 }  // namespace dart