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

chrome/browser/sync/glue/shared_change_processor_ref.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 CHROME_BROWSER_SYNC_GLUE_SHARED_CHANGE_PROCESSOR_REF_H_
 #define CHROME_BROWSER_SYNC_GLUE_SHARED_CHANGE_PROCESSOR_REF_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "chrome/browser/sync/glue/shared_change_processor.h"
 #include "sync/api/sync_change_processor.h"
 #include "sync/api/sync_error_factory.h"
 
 namespace browser_sync {
 
 // A syncer::SyncChangeProcessor stub for interacting with a refcounted
 // SharedChangeProcessor.
 class SharedChangeProcessorRef : public syncer::SyncChangeProcessor,
                                  public syncer::SyncErrorFactory {
  public:
-  SharedChangeProcessorRef(
+  explicit SharedChangeProcessorRef(
       const scoped_refptr<browser_sync::SharedChangeProcessor>&
           change_processor);
   virtual ~SharedChangeProcessorRef();
 
   // syncer::SyncChangeProcessor implementation.
   virtual syncer::SyncError ProcessSyncChanges(
       const tracked_objects::Location& from_here,
       const syncer::SyncChangeList& change_list) OVERRIDE;
 
   // syncer::SyncErrorFactory implementation.
   virtual syncer::SyncError CreateAndUploadError(
       const tracked_objects::Location& from_here,
       const std::string& message) OVERRIDE;
 
   // Default copy and assign welcome (and safe due to refcounted-ness).
 
  private:
   scoped_refptr<browser_sync::SharedChangeProcessor> change_processor_;
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_SHARED_CHANGE_PROCESSOR_REF_H_