Serialize all external strings except for native source code strings.

src/bootstrapper.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/bootstrapper.h"
 
 #include "src/accessors.h"
 #include "src/code-stubs.h"
 #include "src/extensions/externalize-string-extension.h"
 #include "src/extensions/free-buffer-extension.h"
@@ skipping 39 matching lines @@
     // We can use external strings for the natives.
     Vector<const char> source = Natives::GetRawScriptSource(index);
     NativesExternalStringResource* resource =
         new NativesExternalStringResource(this,
                                           source.start(),
                                           source.length());
     // We do not expect this to throw an exception. Change this if it does.
     Handle<String> source_code = isolate_->factory()
                                      ->NewExternalStringFromOneByte(resource)
                                      .ToHandleChecked();
+    // Mark this external string with a special map.
+    source_code->set_map(isolate_->heap()->native_source_string_map());
     heap->natives_source_cache()->set(index, *source_code);
   }
   Handle<Object> cached_source(heap->natives_source_cache()->get(index),
                                isolate_);
   return Handle<String>::cast(cached_source);
 }
 
 
 void Bootstrapper::Initialize(bool create_heap_objects) {
   extensions_cache_.Initialize(isolate_, create_heap_objects);
@@ skipping 2663 matching lines @@
   return from + sizeof(NestingCounterType);
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   DCHECK(!IsActive());
 }
 
 } }  // namespace v8::internal