Convert string16 to base::string16 in content.

content/browser/message_port_service.cc

Index: content/browser/message_port_service.cc
diff --git a/content/browser/message_port_service.cc b/content/browser/message_port_service.cc
index bc2a1ac826f5b68106ea0f6611a28310682f94a0..0d9f6084e8653284943608835e0000b158a82855 100644
--- a/content/browser/message_port_service.cc
+++ b/content/browser/message_port_service.cc
@@ -108,7 +108,7 @@ void MessagePortService::Entangle(int local_message_port_id,
 
 void MessagePortService::PostMessage(
     int sender_message_port_id,
-    const string16& message,
+    const base::string16& message,
     const std::vector<int>& sent_message_port_ids) {
   if (!message_ports_.count(sender_message_port_id)) {
     NOTREACHED();
@@ -130,7 +130,7 @@ void MessagePortService::PostMessage(
 
 void MessagePortService::PostMessageTo(
     int message_port_id,
-    const string16& message,
+    const base::string16& message,
     const std::vector<int>& sent_message_port_ids) {
   if (!message_ports_.count(message_port_id)) {
     NOTREACHED();