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

dbus/bus.cc

Index: dbus/bus.cc
diff --git a/dbus/bus.cc b/dbus/bus.cc
index 30b6cc31cfa8f15a888deba5fd993c1175dfc045..e81cbc8db1d38674c31d6146222ae0e7f71fcc55 100644
--- a/dbus/bus.cc
+++ b/dbus/bus.cc
@@ -28,7 +28,7 @@ namespace {
 // communication.
 class Watch : public base::MessagePumpLibevent::Watcher {
  public:
-  Watch(DBusWatch* watch)
+  explicit Watch(DBusWatch* watch)
       : raw_watch_(watch) {
     dbus_watch_set_data(raw_watch_, this, NULL);
   }
@@ -99,7 +99,7 @@ class Watch : public base::MessagePumpLibevent::Watcher {
 // Bus::OnRemoveTimeout().
 class Timeout : public base::RefCountedThreadSafe<Timeout> {
  public:
-  Timeout(DBusTimeout* timeout)
+  explicit Timeout(DBusTimeout* timeout)
       : raw_timeout_(timeout),
         monitoring_is_active_(false),
         is_completed(false) {