Add [CachedAccessor] attribute to cache (almost) constant accessors (window.document).

third_party/WebKit/Source/bindings/core/v8/WindowProxy.h

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 22 matching lines @@
 
 #include "bindings/core/v8/DOMWrapperWorld.h"
 #include "bindings/core/v8/ScopedPersistent.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "platform/heap/Handle.h"
 #include "platform/weborigin/SecurityOrigin.h"
 #include "wtf/HashMap.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefPtr.h"
 #include "wtf/text/AtomicString.h"
+#include <map>
 #include <v8.h>
 
 namespace blink {
 
 class Frame;
 class HTMLDocument;
 class SecurityOrigin;
 
 // WindowProxy represents all the per-global object state for a Frame that
 // persist between navigations.
@@ skipping 25 matching lines @@
 
     void clearForNavigation();
     void clearForClose();
 
     v8::Local<v8::Object> globalIfNotDetached();
     v8::Local<v8::Object> releaseGlobal();
     void setGlobal(v8::Local<v8::Object>);
 
     DOMWrapperWorld& world() { return *m_world; }
 
+    // Global map, 'name' -> private property for all cached accessors.
+    typedef std::map<std::string, v8::Eternal<v8::Private>> StringPrivateMap;
+    static StringPrivateMap& cachedAccessors()
+    {
+        DCHECK(isMainThread());

[jochen (gone - plz use gerrit), 2016/09/15 08:20:51]

that means that this feature is currently not available to workers, but since
it's on window proxy that's fine I guess

[jochen (gone - plz use gerrit), 2016/09/15 08:20:51]

that means that this feature is currently not available to workers, but since
it's on window proxy that's fine I guess

[Alfonso, 2016/09/16 14:21:48]

Refactor to use V8PrivateProperty to expose private properties, this is no
longer needed/used.

+        DEFINE_STATIC_LOCAL(StringPrivateMap, map, ());

[haraken, 2016/09/15 09:26:10]

If this map is intended to be per-isolate, can you put the map on
V8PerIsolateData? WindowProxy doesn't look like a right place to put it.

That said, as yukishiino@ mentioned, if you can use V8PrivateProperty, that will
be the best solution.

[Alfonso, 2016/09/16 14:21:48]

Done.

+        return map;
+    }
+
 private:
     WindowProxy(Frame*, PassRefPtr<DOMWrapperWorld>, v8::Isolate*);
     bool initialize();
 
     enum GlobalDetachmentBehavior {
         DoNotDetachGlobal,
         DetachGlobal
     };
     void disposeContext(GlobalDetachmentBehavior);
 
@@ skipping 21 matching lines @@
     v8::Isolate* m_isolate;
     RefPtr<ScriptState> m_scriptState;
     RefPtr<DOMWrapperWorld> m_world;
     ScopedPersistent<v8::Object> m_global;
     ScopedPersistent<v8::Object> m_document;
 };
 
 } // namespace blink
 
 #endif // WindowProxy_h