Get rid of ipc_sender.h include in ipc_message.h.

chrome/browser/importer/external_process_importer_bridge.h

Index: chrome/browser/importer/external_process_importer_bridge.h
diff --git a/chrome/browser/importer/external_process_importer_bridge.h b/chrome/browser/importer/external_process_importer_bridge.h
index 7942ab69e9925e1038de1e09937921bd70c478f9..e06ac9d2cf715aea7006702ee0336cea729cf9f0 100644
--- a/chrome/browser/importer/external_process_importer_bridge.h
+++ b/chrome/browser/importer/external_process_importer_bridge.h
@@ -12,7 +12,6 @@
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/importer/importer_bridge.h"
 #include "chrome/browser/importer/profile_writer.h"
-#include "ipc/ipc_message.h"
 
 class GURL;
 
@@ -21,6 +20,11 @@ class DictionaryValue;
 class TaskRunner;
 }
 
+namespace IPC {
+class Message;
+class Sender;
+}
+
 // When the importer is run in an external process, the bridge is effectively
 // split in half by the IPC infrastructure.  The external bridge receives data
 // and notifications from the importer, and sends it across IPC.  The