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

ui/base/dialogs/select_file_dialog_mac.mm

 // 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.
 
 #include "ui/base/dialogs/select_file_dialog.h"
 
 #import <Cocoa/Cocoa.h>
 #include <CoreServices/CoreServices.h>
 
 #include <map>
@@ skipping 43 matching lines @@
 
 // NSSavePanel delegate method
 - (BOOL)panel:(id)sender shouldShowFilename:(NSString *)filename;
 
 @end
 
 // Implementation of SelectFileDialog that shows Cocoa dialogs for choosing a
 // file or folder.
 class SelectFileDialogImpl : public ui::SelectFileDialog {
  public:
-  explicit SelectFileDialogImpl(Listener* listener,
-                                ui::SelectFilePolicy* policy);
+  SelectFileDialogImpl(Listener* listener,
+                       ui::SelectFilePolicy* policy);
 
   // BaseShellDialog implementation.
   virtual bool IsRunning(gfx::NativeWindow parent_window) const;
   virtual void ListenerDestroyed();
 
   // Callback from ObjC bridge.
   void FileWasSelected(NSSavePanel* dialog,
                        NSWindow* parent_window,
                        bool was_cancelled,
                        bool is_multi,
@@ skipping 339 matching lines @@
 
 namespace ui {
 
 SelectFileDialog* CreateMacSelectFileDialog(
     SelectFileDialog::Listener* listener,
     SelectFilePolicy* policy) {
   return new SelectFileDialogImpl(listener, policy);
 }
 
 }  // namespace ui