Turned UiStrings into a singleton so that the continue window does not depend on ChromotingHost.

remoting/host/chromoting_host.cc

Index: remoting/host/chromoting_host.cc
diff --git a/remoting/host/chromoting_host.cc b/remoting/host/chromoting_host.cc
index 9216fb0598df98e904c69676dd877686885b48b3..4776d7375e9dea5ef9939debc9a5d16103a20bc9 100644
--- a/remoting/host/chromoting_host.cc
+++ b/remoting/host/chromoting_host.cc
@@ -373,13 +373,6 @@ void ChromotingHost::DisconnectAllClients() {
   }
 }
 
-void ChromotingHost::SetUiStrings(const UiStrings& ui_strings) {
-  DCHECK(network_task_runner_->BelongsToCurrentThread());
-  DCHECK_EQ(state_, kInitial);
-
-  ui_strings_ = ui_strings;
-}
-
 void ChromotingHost::OnClientStopped() {
   DCHECK(network_task_runner_->BelongsToCurrentThread());