Add missing (and remove superfluous) 'explicit' from constructors.

remoting/protocol/clipboard_echo_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_ECHO_FILTER_H_
 #define REMOTING_PROTOCOL_CLIPBOARD_ECHO_FILTER_H_
 
 #include <map>
 #include <string>
 
@@ skipping 20 matching lines @@
   // client.
   ClipboardStub* client_filter();
 
   // Gets the ClipboardStub that sends events through this filter and on to the
   // host.
   ClipboardStub* host_filter();
 
  private:
   class ClientFilter : public ClipboardStub {
    public:
-    ClientFilter(ClipboardEchoFilter* filter);
+    explicit ClientFilter(ClipboardEchoFilter* filter);
     virtual void InjectClipboardEvent(const ClipboardEvent& event) OVERRIDE;
 
    private:
     ClipboardEchoFilter* filter_;
   };
 
   class HostFilter : public ClipboardStub {
    public:
-    HostFilter(ClipboardEchoFilter* filter);
+    explicit HostFilter(ClipboardEchoFilter* filter);
     virtual void InjectClipboardEvent(const ClipboardEvent& event) OVERRIDE;
 
    private:
     ClipboardEchoFilter* filter_;
   };
 
   void InjectClipboardEventToHost(const ClipboardEvent& event);
   void InjectClipboardEventToClient(const ClipboardEvent& event);
 
   ClipboardStub* host_stub_;
   ClipboardStub* client_stub_;
   ClientFilter client_filter_;
   HostFilter host_filter_;
 
   // The latest item received from the client.
   std::string client_latest_mime_type_;
   std::string client_latest_data_;
 
   DISALLOW_COPY_AND_ASSIGN(ClipboardEchoFilter);
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_CLIPBOARD_ECHO_FILTER_H_