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

chrome/browser/ui/cocoa/first_run_dialog.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.
 
 #import "chrome/browser/ui/cocoa/first_run_dialog.h"
 
 #include "base/bind.h"
 #include "base/mac/bundle_locations.h"
 #include "base/mac/mac_util.h"
 #include "base/memory/ref_counted.h"
@@ skipping 36 matching lines @@
   if (y1 < y2)
     return NSOrderedAscending;
   else if (y1 > y2)
     return NSOrderedDescending;
   else
     return NSOrderedSame;
 }
 
 class FirstRunShowBridge : public base::RefCounted<FirstRunShowBridge> {
  public:
-  FirstRunShowBridge(FirstRunDialogController* controller);
+  explicit FirstRunShowBridge(FirstRunDialogController* controller);
 
   void ShowDialog();
 
  private:
   friend class base::RefCounted<FirstRunShowBridge>;
 
   ~FirstRunShowBridge();
 
   FirstRunDialogController* controller_;
 };
@@ skipping 218 matching lines @@
   [NSApp stopModal];
 }
 
 - (IBAction)learnMore:(id)sender {
   NSString* urlStr = base::SysUTF8ToNSString(chrome::kLearnMoreReportingURL);
   NSURL* learnMoreUrl = [NSURL URLWithString:urlStr];
   [[NSWorkspace sharedWorkspace] openURL:learnMoreUrl];
 }
 
 @end