Add a comment about calling clearScriptObjects before clearForNavigation.

Source/bindings/core/v8/ScriptController.cpp

 /*
  * Copyright (C) 2008, 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Opera Software ASA. 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
@@ skipping 403 matching lines @@
         return createNoScriptObject();
 
     return npCreateV8ScriptObject(0, v8::Handle<v8::Object>::Cast(v8plugin), window, scriptState->isolate());
 }
 
 void ScriptController::clearWindowShell()
 {
     double start = currentTime();
     // V8 binding expects ScriptController::clearWindowShell only be called
     // when a frame is loading a new page. This creates a new context for the new page.
+
+    // The V8 context must be available for |clearScriptObjects()|.
+    // The below call must be before |clearForNavigation()| which disposes the V8 context.
     clearScriptObjects();
     m_windowShell->clearForNavigation();
     for (IsolatedWorldMap::iterator iter = m_isolatedWorlds.begin(); iter != m_isolatedWorlds.end(); ++iter)
         iter->value->clearForNavigation();
     blink::Platform::current()->histogramCustomCounts("WebCore.ScriptController.clearWindowShell", (currentTime() - start) * 1000, 0, 10000, 50);
 }
 
 void ScriptController::setCaptureCallStackForUncaughtExceptions(bool value)
 {
     v8::V8::SetCaptureStackTraceForUncaughtExceptions(value, ScriptCallStack::maxCallStackSizeToCapture, stackTraceOptions);
@@ skipping 201 matching lines @@
         resultArray->Set(i, evaluationResult);
     }
 
     if (results) {
         for (size_t i = 0; i < resultArray->Length(); ++i)
             results->append(handleScope.Escape(resultArray->Get(i)));
     }
 }
 
 } // namespace blink