Move the Kernel string offsets into the VM's heap.

runtime/vm/bootstrap.cc

 // Copyright (c) 2012, 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/bootstrap.h"
 
 #include "include/dart_api.h"
 
 #include "vm/bootstrap_natives.h"
 #include "vm/class_finalizer.h"
@@ skipping 349 matching lines @@
 
   // Load the bootstrap libraries in order (see object_store.h).
   Library& library = Library::Handle(zone);
   String& dart_name = String::Handle(zone);
   for (intptr_t i = 0; i < kBootstrapLibraryCount; ++i) {
     ObjectStore::BootstrapLibraryId id = bootstrap_libraries[i].index;
     library = isolate->object_store()->bootstrap_library(id);
     dart_name = library.url();
     for (intptr_t j = 0; j < program->libraries().length(); ++j) {
       kernel::Library* kernel_library = program->libraries()[j];
-      kernel::String* uri = kernel_library->import_uri();
-      const String& kernel_name = reader.DartSymbol(uri);
+      intptr_t uri_index = kernel_library->import_uri();
+      const String& kernel_name = reader.DartSymbol(uri_index);
       if (kernel_name.Equals(dart_name)) {
         reader.ReadLibrary(kernel_library);
         library.SetLoaded();
         break;
       }
     }
   }
 
   // Finish bootstrapping, including class finalization.
   Finish(thread, /*from_kernel=*/true);
@@ skipping 38 matching lines @@
       lib.Register(thread);
       isolate->object_store()->set_bootstrap_library(id, lib);
     }
   }
 
   return (kernel_program == NULL) ? BootstrapFromSource(thread)
                                   : BootstrapFromKernel(thread, kernel_program);
 }
 
 }  // namespace dart