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

base/callback_unittest.cc

 // 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 "base/bind.h"
 #include "base/callback.h"
 #include "base/callback_helpers.h"
 #include "base/callback_internal.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 130 matching lines @@
   TestForReentrancy tfr;
   ASSERT_FALSE(tfr.cb.is_null());
   ASSERT_FALSE(tfr.cb_already_run);
   ResetAndReturn(&tfr.cb).Run();
   ASSERT_TRUE(tfr.cb.is_null());
   ASSERT_TRUE(tfr.cb_already_run);
 }
 
 class CallbackOwner : public base::RefCounted<CallbackOwner> {
  public:
-  CallbackOwner(bool* deleted) {
+  explicit CallbackOwner(bool* deleted) {
     callback_ = Bind(&CallbackOwner::Unused, this);
     deleted_ = deleted;
   }
   void Reset() {
     callback_.Reset();
     // We are deleted here if no-one else had a ref to us.
   }
 
  private:
   friend class base::RefCounted<CallbackOwner>;
@@ skipping 10 matching lines @@
 
 TEST_F(CallbackTest, CallbackHasLastRefOnContainingObject) {
   bool deleted = false;
   CallbackOwner* owner = new CallbackOwner(&deleted);
   owner->Reset();
   ASSERT_TRUE(deleted);
 }
 
 }  // namespace
 }  // namespace base