Add base:: to string16s in win8/.

win8/viewer/metro_viewer_process_host.h

Index: win8/viewer/metro_viewer_process_host.h
diff --git a/win8/viewer/metro_viewer_process_host.h b/win8/viewer/metro_viewer_process_host.h
index ad034ada07f578d1452df11f8b5531c3b6716f02..e156226e86f2fc6b644d5d5348cb3aa3d6b9749a 100644
--- a/win8/viewer/metro_viewer_process_host.h
+++ b/win8/viewer/metro_viewer_process_host.h
@@ -66,12 +66,12 @@ class MetroViewerProcessHost : public IPC::Listener,
 
   // Called over IPC by the viewer process to request that the url passed in be
   // opened.
-  virtual void OnOpenURL(const string16& url) = 0;
+  virtual void OnOpenURL(const base::string16& url) = 0;
 
   // Called over IPC by the viewer process to request that the search string
   // passed in is passed to the default search provider and a URL navigation be
   // performed.
-  virtual void OnHandleSearchRequest(const string16& search_string) = 0;
+  virtual void OnHandleSearchRequest(const base::string16& search_string) = 0;
 
   // Called over IPC by the viewer process when the window size has changed.
   virtual void OnWindowSizeChanged(uint32 width, uint32 height) = 0;