Use phantom handles instead of weak handles

Phantom handles allow for freeing objects with one pass of GC. However,
this means that by the time the callback is invoked, the v8 object already
does no longer exist. To avoid accidential access to the dead object, there
are now two callbacks, where the first must only reset the handle, and the
second does the clean-up work.

R=tsepez@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1129253004

1 files changed, 18 insertions, 9 deletions

diff --git a/fpdfsdk/src/javascript/JS_Object.cpp b/fpdfsdk/src/javascript/JS_Object.cpp
index 6c0c868e4c..66fd2b682f 100644
--- a/fpdfsdk/src/javascript/JS_Object.cpp
+++ b/fpdfsdk/src/javascript/JS_Object.cpp
@@ -88,16 +88,19 @@ void CJS_EmbedObj::EndTimer(CJS_Timer* pTimer)
 }
 
 /* ---------------------------------  CJS_Object --------------------------------- */
-void  FreeObject(const v8::WeakCallbackData<v8::Object, CJS_Object>& data)
+void  FreeObject(const v8::WeakCallbackInfo<CJS_Object>& data)
 {
 	CJS_Object* pJSObj  = data.GetParameter();
-	if(pJSObj)
-	{
-		pJSObj->ExitInstance();
-		delete pJSObj;
-	}
-	v8::Local<v8::Object> obj = data.GetValue();
-	JS_FreePrivate(obj);
+        pJSObj->ExitInstance();
+        delete pJSObj;
+	JS_FreePrivate(data.GetInternalField(0));
+}
+
+void  DisposeObject(const v8::WeakCallbackInfo<CJS_Object>& data)
+{
+	CJS_Object* pJSObj  = data.GetParameter();
+        pJSObj->Dispose();
+        data.SetSecondPassCallback(FreeObject);
 }
 
 CJS_Object::CJS_Object(JSFXObject pObject) :m_pEmbedObj(NULL)
@@ -117,7 +120,13 @@ CJS_Object::~CJS_Object(void)
 
 void	CJS_Object::MakeWeak()
 {
-	m_pObject.SetWeak(this, FreeObject);
+	m_pObject.SetWeak(
+            this, DisposeObject, v8::WeakCallbackType::kInternalFields);
+}
+
+void    CJS_Object::Dispose()
+{
+        m_pObject.Reset();
 }
 
 CPDFSDK_PageView* CJS_Object::JSGetPageView(IFXJS_Context* cc)