[Offline Pages] Minor fix for log messages in event logger.

components/offline_pages/core/offline_event_logger.cc

 // Copyright 2016 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/strings/stringprintf.h"
 #include "base/time/time.h"
 #include "components/offline_pages/core/offline_event_logger.h"
 
 namespace offline_pages {
 
@@ skipping 26 matching lines @@
     return;
 
   base::Time::Exploded current_time;
   base::Time::Now().LocalExplode(&current_time);
 
   std::string date_string = base::StringPrintf(
       "%d %02d %02d %02d:%02d:%02d", current_time.year, current_time.month,
       current_time.day_of_month, current_time.hour, current_time.minute,
       current_time.second);
 
-  std::string log_message = date_string + ": " + activity;
   if (client_)
-    client_->CustomLog(log_message);
+    client_->CustomLog(activity);
 
   if (activities_.size() == kMaxLogCount)
     activities_.pop_back();
 
-  activities_.push_front(log_message);
+  activities_.push_front(date_string + ": " + activity);
 }
 
 void OfflineEventLogger::SetClient(Client* client) {
   DCHECK(client);
   SetIsLogging(true);
   client_ = client;
 }
 
 }  // namespace offline_pages