[wrapper-tracing] Add heap snapshot generator infrastructure

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

 /*
  * Copyright (C) 2010 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 28 matching lines @@
 #include "wtf/TypeTraits.h"
 #include <v8.h>
 
 namespace blink {
 
 class CORE_EXPORT TraceWrapperBase {
   WTF_MAKE_NONCOPYABLE(TraceWrapperBase);
 
  public:
   TraceWrapperBase() = default;
+  virtual bool isScriptWrappable() const { return false; }
 
   DECLARE_VIRTUAL_TRACE_WRAPPERS(){};
 };
 
 // ScriptWrappable provides a way to map from/to C++ DOM implementation to/from
 // JavaScript object (platform object).  ToV8() converts a ScriptWrappable to
 // a v8::Object and toScriptWrappable() converts a v8::Object back to
 // a ScriptWrappable.  v8::Object as platform object is called "wrapper object".
 // The wrapepr object for the main world is stored in ScriptWrappable.  Wrapper
 // objects for other worlds are stored in DOMWrapperMap.
 class CORE_EXPORT ScriptWrappable : public TraceWrapperBase {
   WTF_MAKE_NONCOPYABLE(ScriptWrappable);
 
  public:
   ScriptWrappable() {}
 
+  bool isScriptWrappable() const override { return true; }
+
   template <typename T>
   T* toImpl() {
     // All ScriptWrappables are managed by the Blink GC heap; check that
     // |T| is a garbage collected type.
     static_assert(
         sizeof(T) && WTF::IsGarbageCollectedType<T>::value,
         "Classes implementing ScriptWrappable must be garbage collected.");
 
 // Check if T* is castable to ScriptWrappable*, which means T doesn't
 // have two or more ScriptWrappable as superclasses. If T has two
@@ skipping 84 matching lines @@
   bool containsWrapper() const { return !m_mainWorldWrapper.IsEmpty(); }
 
   //  Mark wrapper of this ScriptWrappable as alive in V8. Only marks
   //  wrapper in the main world. To mark wrappers in all worlds call
   //  ScriptWrappableVisitor::markWrapper(ScriptWrappable*, v8::Isolate*)
   void markWrapper(const WrapperVisitor*) const;
 
  private:
   // These classes are exceptionally allowed to use mainWorldWrapper().
   friend class DOMDataStore;
+  friend class HeapSnaphotWrapperVisitor;
   friend class V8HiddenValue;
   friend class V8PrivateProperty;
   friend class WebGLRenderingContextBase;
 
   v8::Local<v8::Object> mainWorldWrapper(v8::Isolate* isolate) const {
     return v8::Local<v8::Object>::New(isolate, m_mainWorldWrapper);
   }
 
+  // Only use when really necessary, i.e., when passing over this
+  // ScriptWrappable's reference to V8. Should only be needed by GC
+  // infrastructure.
+  const v8::Persistent<v8::Object>* rawMainWorldWrapper() const {
+    return &m_mainWorldWrapper;
+  }
+
   v8::Persistent<v8::Object> m_mainWorldWrapper;
 };
 
 // Defines 'wrapperTypeInfo' virtual method which returns the WrapperTypeInfo of
 // the instance. Also declares a static member of type WrapperTypeInfo, of which
 // the definition is given by the IDL code generator.
 //
 // All the derived classes of ScriptWrappable, regardless of directly or
 // indirectly, must write this macro in the class definition as long as the
 // class has a corresponding .idl file.
@@ skipping 19 matching lines @@
 #define DECLARE_WRAPPERTYPEINFO()                          \
  public:                                                   \
   const WrapperTypeInfo* wrapperTypeInfo() const override; \
                                                            \
  private:                                                  \
   typedef void end_of_define_wrappertypeinfo_not_reached_t
 
 }  // namespace blink
 
 #endif  // ScriptWrappable_h