[Bindings] Specialize WindowDocument symbol in V8PrivateProperty

third_party/WebKit/Source/bindings/core/v8/V8PrivateProperty.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8PrivateProperty_h
 #define V8PrivateProperty_h
 
 #include <memory>
 
 #include "bindings/core/v8/ScriptPromiseProperties.h"
@@ skipping 21 matching lines @@
   X(IDBObserver, Callback)                            \
   X(IntersectionObserver, Callback)                   \
   X(MessageEvent, CachedData)                         \
   X(MutationObserver, Callback)                       \
   X(NamedConstructor, Initialized)                    \
   X(PerformanceObserver, Callback)                    \
   X(SameObject, NotificationActions)                  \
   X(SameObject, NotificationData)                     \
   X(SameObject, NotificationVibrate)                  \
   X(SameObject, PerformanceLongTaskTimingAttribution) \
-  X(V8NodeFilterCondition, Filter)                    \
-  X(Window, DocumentCachedAccessor)
+  X(V8NodeFilterCondition, Filter)
 
 // The getter's name for a private property.
 #define V8_PRIVATE_PROPERTY_GETTER_NAME(InterfaceName, PrivateKeyName) \
   get##InterfaceName##PrivateKeyName
 
 // The member variable's name for a private property.
 #define V8_PRIVATE_PROPERTY_MEMBER_NAME(InterfaceName, PrivateKeyName) \
   m_symbol##InterfaceName##PrivateKeyName
 
 // The string used to create a private symbol.  Must be unique per V8 instance.
@@ skipping 104 matching lines @@
   }
   V8_PRIVATE_PROPERTY_FOR_EACH(V8_PRIVATE_PROPERTY_DEFINE_GETTER)
 #undef V8_PRIVATE_PROPERTY_DEFINE_GETTER
 
   static Symbol createSymbol(v8::Isolate* isolate,
                              const char* symbol,
                              size_t length) {
     return Symbol(createV8Private(isolate, symbol, length));
   }
 
+  static Symbol getWindowDocumentCachedAccessor(v8::Isolate* isolate) {
+    static constexpr char kSymbol[] = "Window#Document";

[Yuki, 2017/03/27 09:06:18]

nit: Window#document?

[peria, 2017/03/28 08:10:03]

Done.
This string was created with 
  V8_PRIVATE_PROPERTY_SYMBOL_STRING(Window, DocumentCachedAccessor),
so it should be "Window#DocumentCachedAccessor" to be consistent.

+    V8PrivateProperty* privateProp =
+        V8PerIsolateData::from(isolate)->privateProperty();
+    if (UNLIKELY(privateProp->m_symbolWindowDocument.isEmpty())) {
+      privateProp->m_symbolWindowDocument.set(
+          isolate, createV8Private(isolate, kSymbol, sizeof(kSymbol)));
+    }
+    return Symbol(privateProp->m_symbolWindowDocument.newLocal(isolate));
+  }
+
  private:
   V8PrivateProperty() {}
 
   static v8::Local<v8::Private> createV8Private(v8::Isolate*,
                                                 const char* symbol,
                                                 size_t length);
 
 #define V8_PRIVATE_PROPERTY_DECLARE_MEMBER(InterfaceName, KeyName) \
   v8::Eternal<v8::Private> V8_PRIVATE_PROPERTY_MEMBER_NAME(        \
       InterfaceName, KeyName);  // NOLINT(readability/naming/underscores)
   V8_PRIVATE_PROPERTY_FOR_EACH(V8_PRIVATE_PROPERTY_DECLARE_MEMBER)
 #undef V8_PRIVATE_PROPERTY_DECLARE_MEMBER
+
+  // TODO(peria): Do not use specialized hack for Window#Document.

[Yuki, 2017/03/27 09:06:18]

nit: Window#document or [Ww]indow.document?

[haraken, 2017/03/27 09:49:56]

a special hack

[peria, 2017/03/28 08:10:03]

Done.

[peria, 2017/03/28 08:10:03]

Done.

+  // This is required to put v8::Private key in snapshot, and it cannot

[haraken, 2017/03/27 09:49:56]

in a snapshot

[peria, 2017/03/28 08:10:03]

Done.

+  // be a v8::Eternal<> due to V8 serializer's requirement.
+  ScopedPersistent<v8::Private> m_symbolWindowDocument;

[jbroman, 2017/03/27 18:06:56]

Can you explain to me why this is correct? If I understand correctly, the
problem is that the context snapshot serializer doesn't walk the eternal
handles, right?

What causes |m_symbolWindowDocument| to actually match the v8::Private that
comes from the snapshot? At first glance, it looks to me like
|m_symbolWindowDocument| won't be set, and so after loading the snapshot will
point to a different private symbol than the one referred to by the window DOM
template. (If these refer to different symbols, the invalidation mechanism won't
be correct.)

[peria, 2017/03/28 08:10:03]

Right. The difference between v8::Eternal<> and ScopedPersistent is
that ScopedPersistent can be removed, while v8::Eternal<> can't.
This was my mistake in PS1. We have to use Private::ForApi to get the same
v8::Private symbol. V8 caches created Private symbols and ForApi() returns
cached one with the key string and isolate.

[Yuki, 2017/03/28 08:17:59]

I'm okay to use ForApi as a short-term solution, but we'd like to avoid using
this API for future, I think.  We need to come up with another idea.

 };
 
 }  // namespace blink
 
 #endif  // V8PrivateProperty_h