Make it clear what last_sync_timestamp actually tracks. Update

chrome/common/ipc_test_sink.h

 // Copyright (c) 2009 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.
 
 #ifndef CHROME_COMMON_IPC_TEST_SINK_H_
 #define CHROME_COMMON_IPC_TEST_SINK_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 21 matching lines @@
 //   IPC::Message* msg = test_sink.GetFirstMessageMatching(ViewMsg_Foo::ID));
 //   ASSERT_TRUE(msg);
 //   bool first_param;
 //   int second_param;
 //   ViewMsg_Foo::Read(msg, &first_param, &second_param);
 //
 //   // Go on to the next phase of the test.
 //   test_sink.ClearMessages();
 //
 // To hook up the sink, all you need to do is call OnMessageReceived when a
-// message is recieved.
+// message is received.
 class TestSink {
  public:
   TestSink();
   ~TestSink();
 
   // Used by the source of the messages to send the message to the sink. This
   // will make a copy of the message and store it in the list.
   void OnMessageReceived(const Message& msg);
 
   // Returns the number of messages in the queue.
@@ skipping 22 matching lines @@
  private:
   // The actual list of received messages.
   std::vector<Message> messages_;
 
   DISALLOW_COPY_AND_ASSIGN(TestSink);
 };
 
 }  // namespace IPC
 
 #endif  // CHROME_COMMON_IPC_TEST_SINK_H_