Revert of Reland: Make the CPDFXFA_App non-global

fxjs/fxjs_v8.h

Index: fxjs/fxjs_v8.h
diff --git a/fxjs/fxjs_v8.h b/fxjs/fxjs_v8.h
index ba729626f245a542395cffc9bab624c34c71a244..5f658989a57ab350e3d17fd217df3dcef85c2338 100644
--- a/fxjs/fxjs_v8.h
+++ b/fxjs/fxjs_v8.h
@@ -138,6 +138,13 @@
 
   static CFXJS_Engine* CurrentEngineFromIsolate(v8::Isolate* pIsolate);
   static int GetObjDefnID(v8::Local<v8::Object> pObj);
+
+#ifdef PDF_ENABLE_XFA
+  // Called as part of FXJS_InitializeEngine, exposed so PDF can make its
+  // own contexts compatible with XFA or vice versa.
+  static void SetForV8Context(v8::Local<v8::Context> v8Context,
+                              CFXJS_Engine* pEngine);
+#endif  // PDF_ENABLE_XFA
 
   v8::Isolate* GetIsolate() const { return m_isolate; }