Bind Window focus ability to the ExecutionContext instead of the process.

Source/core/dom/ExecutionContext.h

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2012 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 118 matching lines @@
     void enforceSandboxFlags(SandboxFlags mask);
 
     PassOwnPtr<LifecycleNotifier<ExecutionContext> > createLifecycleNotifier();
 
     virtual EventTarget* errorEventTarget() = 0;
     virtual EventQueue* eventQueue() const = 0;
 
     void enforceStrictMixedContentChecking() { m_strictMixedContentCheckingEnforced = true; }
     bool shouldEnforceStrictMixedContentChecking() const { return m_strictMixedContentCheckingEnforced; }
 
+    void allowWindowFocus();
+    void consumeWindowFocus();
+    bool isWindowFocusAllowed() const;
+
 protected:
     ExecutionContext();
     virtual ~ExecutionContext();
 
     virtual const KURL& virtualURL() const = 0;
     virtual KURL virtualCompleteURL(const String&) const = 0;
 
     ContextLifecycleNotifier& lifecycleNotifier();
 
 private:
@@ skipping 26 matching lines @@
     bool m_activeDOMObjectsAreStopped;
 
     OwnPtrWillBeMember<PublicURLManager> m_publicURLManager;
 
     bool m_strictMixedContentCheckingEnforced;
 
     // The location of this member is important; to make sure contextDestroyed() notification on
     // ExecutionContext's members (notably m_timeouts) is called before they are destructed,
     // m_lifecycleNotifer should be placed *after* such members.
     OwnPtr<ContextLifecycleNotifier> m_lifecycleNotifier;
+
+    // Counter that keeps track of how many window focus calls are allowed for
+    // this ExecutionContext. Callers are expected to call |allowWindowFocus()|
+    // and |consumeWindowFocus()| in order to increment and decrement the
+    // counter.
+    int m_windowFocusTokens;
 };
 
 } // namespace blink
 
 #endif // ExecutionContext_h