Run LocalizeStrings() on plugin thread.

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 9172ada94d6d48e908c7b1b1c48aa15e7e5f3ec7..e6ed3cff9793d79456858befbe08d64155a2acd0 100644
--- a/remoting/host/plugin/host_script_object.h
+++ b/remoting/host/plugin/host_script_object.h
@@ -12,6 +12,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/cancellation_flag.h"
+#include "base/synchronization/lock.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/string16.h"
 #include "base/threading/platform_thread.h"
@@ -20,6 +21,7 @@
 #include "remoting/host/chromoting_host_context.h"
 #include "remoting/host/host_status_observer.h"
 #include "remoting/host/plugin/host_plugin_utils.h"
+#include "remoting/host/ui_strings.h"
 #include "third_party/npapi/bindings/npapi.h"
 #include "third_party/npapi/bindings/npfunctions.h"
 #include "third_party/npapi/bindings/npruntime.h"
@@ -167,6 +169,9 @@ class HostNPScriptObject : public HostStatusObserver {
   scoped_refptr<ChromotingHost> host_;
   int failed_login_attempts_;
 
+  UiStrings ui_strings_;
+  base::Lock ui_strings_lock_;
+
   base::WaitableEvent disconnected_event_;
 
   scoped_ptr<policy_hack::NatPolicy> nat_policy_;