ScriptState::contextIsEmpty shouldn't return true for a context whose global object is detached

Source/bindings/core/v8/custom/V8WindowCustom.cpp

Index: Source/bindings/core/v8/custom/V8WindowCustom.cpp
diff --git a/Source/bindings/core/v8/custom/V8WindowCustom.cpp b/Source/bindings/core/v8/custom/V8WindowCustom.cpp
index 242bcccca3cad89a1beecc2b90207cd919e11c19..21aaf9ca78f82806e7c851e7d4f615a25a32ed12 100644
--- a/Source/bindings/core/v8/custom/V8WindowCustom.cpp
+++ b/Source/bindings/core/v8/custom/V8WindowCustom.cpp
@@ -334,7 +334,7 @@ v8::Handle<v8::Value> DialogHandler::returnValue() const
 {
     if (!m_scriptStateForDialogFrame)
         return v8Undefined();
-    ASSERT(!m_scriptStateForDialogFrame->contextIsEmpty());
+    ASSERT(!m_scriptStateForDialogFrame->contextIsValue());
 
     v8::Isolate* isolate = m_scriptStateForDialogFrame->isolate();
     v8::EscapableHandleScope handleScope(isolate);