Convert string16 to base::string16 in content.

content/public/browser/browser_plugin_guest_delegate.h

Index: content/public/browser/browser_plugin_guest_delegate.h
diff --git a/content/public/browser/browser_plugin_guest_delegate.h b/content/public/browser/browser_plugin_guest_delegate.h
index e8767e20768856291be8215bd2a6aed9b454b891..fd535df679c311a59a54297451d1fa0f39f6314f 100644
--- a/content/public/browser/browser_plugin_guest_delegate.h
+++ b/content/public/browser/browser_plugin_guest_delegate.h
@@ -26,9 +26,9 @@ class CONTENT_EXPORT BrowserPluginGuestDelegate {
 
   // Add a message to the console.
   virtual void AddMessageToConsole(int32 level,
-                                   const string16& message,
+                                   const base::string16& message,
                                    int32 line_no,
-                                   const string16& source_id) {}
+                                   const base::string16& source_id) {}
 
   // Request the delegate to close this guest, and do whatever cleanup it needs
   // to do.