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

base/message_pump_libevent_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/message_pump_libevent.h"
 
 #include <unistd.h>
 
 #include "base/message_loop.h"
 #include "base/posix/eintr_wrapper.h"
@@ skipping 67 matching lines @@
   ASSERT_DEATH(io_loop()->WatchFileDescriptor(
       STDOUT_FILENO, false, MessageLoopForIO::WATCH_READ, &watcher, &delegate),
       "Check failed: "
       "watch_file_descriptor_caller_checker_.CalledOnValidThread()");
 }
 
 #endif  // GTEST_HAS_DEATH_TEST && !defined(NDEBUG)
 
 class BaseWatcher : public MessagePumpLibevent::Watcher {
  public:
-  BaseWatcher(MessagePumpLibevent::FileDescriptorWatcher* controller)
+  explicit BaseWatcher(MessagePumpLibevent::FileDescriptorWatcher* controller)
       : controller_(controller) {
     DCHECK(controller_);
   }
   virtual ~BaseWatcher() {}
 
   // base:MessagePumpLibevent::Watcher interface
   virtual void OnFileCanReadWithoutBlocking(int /* fd */) OVERRIDE {
     NOTREACHED();
   }
 
@@ skipping 54 matching lines @@
   pump->WatchFileDescriptor(pipefds_[1],
       false, MessagePumpLibevent::WATCH_READ_WRITE, &watcher, &delegate);
 
   // Spoof a libevent notification.
   OnLibeventNotification(pump, &watcher);
 }
 
 }  // namespace
 
 }  // namespace base