views: Mark single-argument constructors as explicit.

ui/views/controls/menu/menu_model_adapter_unittest.cc

Index: ui/views/controls/menu/menu_model_adapter_unittest.cc
diff --git a/ui/views/controls/menu/menu_model_adapter_unittest.cc b/ui/views/controls/menu/menu_model_adapter_unittest.cc
index 4b35883a23334ce7093c40d5478a0fa36bed231e..ba6d40658d4b7cf11bb3e95f6e996a8b243104ed 100644
--- a/ui/views/controls/menu/menu_model_adapter_unittest.cc
+++ b/ui/views/controls/menu/menu_model_adapter_unittest.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// 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.
 
@@ -24,8 +24,9 @@ const int kFirstItemIndex = 25;
 
 class MenuModelBase : public ui::MenuModel {
  public:
-  MenuModelBase(int command_id_base) : command_id_base_(command_id_base),
-                                       last_activation_(-1) {
+  explicit MenuModelBase(int command_id_base)
+      : command_id_base_(command_id_base),
+        last_activation_(-1) {
   }
 
   virtual ~MenuModelBase() {