Introduce "underlying types" to abstract XFA differences.

fpdfsdk/src/javascript/JS_Runtime.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "JS_Runtime.h"
 
 #include "../../../xfa/src/fxjse/src/value.h"
 #include "../../include/fpdfxfa/fpdfxfa_app.h"
@@ skipping 75 matching lines @@
 
   CJS_Context* pContext = (CJS_Context*)NewContext();
   FXJS_InitializeRuntime(GetIsolate(), this, &m_context, &m_StaticObjects);
   ReleaseContext(pContext);
 }
 
 CJS_Runtime::~CJS_Runtime() {
   for (auto* obs : m_observers)
     obs->OnDestroyed();
 
-  for (int i = 0; i < m_ContextArray.GetSize(); i++)
+  for (int i = 0, sz = m_ContextArray.GetSize(); i < sz; i++)
     delete m_ContextArray.GetAt(i);
 
   m_ContextArray.RemoveAll();
 
   m_pApp = NULL;
   m_pDocument = NULL;
   m_context.Reset();
 
   if (m_isolateManaged)
     m_isolate->Dispose();
@@ skipping 188 matching lines @@
 
 void CJS_Runtime::AddObserver(Observer* observer) {
   ASSERT(m_observers.find(observer) == m_observers.end());
   m_observers.insert(observer);
 }
 
 void CJS_Runtime::RemoveObserver(Observer* observer) {
   ASSERT(m_observers.find(observer) != m_observers.end());
   m_observers.erase(observer);
 }