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

remoting/protocol/clipboard_filter.h

Index: remoting/protocol/clipboard_filter.h
diff --git a/remoting/protocol/clipboard_filter.h b/remoting/protocol/clipboard_filter.h
index 5fbcda5a15b7d2813be0e2d26786974747a600a3..0cae152f965ec82c92e1ff3209a329314f2e7c87 100644
--- a/remoting/protocol/clipboard_filter.h
+++ b/remoting/protocol/clipboard_filter.h
@@ -12,21 +12,28 @@
 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);
 };