Allow input & clipboard filters to be disabled without NULLing target stub.

remoting/protocol/clipboard_filter.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef REMOTING_PROTOCOL_CLIPBOARD_FILTER_H_
 #define REMOTING_PROTOCOL_CLIPBOARD_FILTER_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "remoting/protocol/clipboard_stub.h"
 
 namespace remoting {
 namespace protocol {
 
-// Forwards clipboard events to |clipboard_stub|, iff |clipboard_stub| is not
-// NULL.
+// Forwards clipboard events to |clipboard_stub|, if configured.  Event
+// forwarding may also be disabled independently of the configured
+// |clipboard_stub|. ClipboardFilters initially have event forwarding enabled.
 class ClipboardFilter : public ClipboardStub {
  public:
   ClipboardFilter();
+  explicit ClipboardFilter(ClipboardStub* clipboard_stub);
   virtual ~ClipboardFilter();
 
   // Set the ClipboardStub that events will be forwarded to.
   void set_clipboard_stub(ClipboardStub* clipboard_stub);
 
+  // Enable/disable forwarding of clipboard events to the ClipboardStub.
+  void set_enabled(bool enabled) { enabled_ = enabled; }
+  bool enabled() const { return enabled_; }
+
   // ClipboardStub interface.
   virtual void InjectClipboardEvent(const ClipboardEvent& event) OVERRIDE;
 
  private:
   ClipboardStub* clipboard_stub_;
+  bool enabled_;
 
   DISALLOW_COPY_AND_ASSIGN(ClipboardFilter);
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_CLIPBOARD_FILTER_H_