Make ChromotingHost::ui_strings() immutable.

remoting/host/plugin/host_script_object.h

Index: remoting/host/plugin/host_script_object.h
diff --git a/remoting/host/plugin/host_script_object.h b/remoting/host/plugin/host_script_object.h
index 04a35b49d03d8744ee13ef0c2652f4e03c77b6ec..9172ada94d6d48e908c7b1b1c48aa15e7e5f3ec7 100644
--- a/remoting/host/plugin/host_script_object.h
+++ b/remoting/host/plugin/host_script_object.h
@@ -13,6 +13,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/cancellation_flag.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/string16.h"
 #include "base/threading/platform_thread.h"
 #include "base/time.h"
 #include "remoting/base/plugin_message_loop_proxy.h"
@@ -135,8 +136,7 @@ class HostNPScriptObject : public HostStatusObserver {
   // a string->string mapping with one optional substitution parameter. Stores
   // the translation in |result| and returns true on success, or leaves it
   // unchanged and returns false on failure.
-  bool LocalizeString(const char* tag, const char* substitution,
-                      std::string* result);
+  bool LocalizeString(const char* tag, string16* result);
 
   // Helper function for executing InvokeDefault on an NPObject, and ignoring
   // the return value.