SurfaceAggregator should check whether output is secure when drawin

cc/trees/proxy_main.cc

Index: cc/trees/proxy_main.cc
diff --git a/cc/trees/proxy_main.cc b/cc/trees/proxy_main.cc
index 07294e8e284921496496a7a4684ac283df1fd65b..c8fa4e28a049d2a5f59845e1292f2848250033d5 100644
--- a/cc/trees/proxy_main.cc
+++ b/cc/trees/proxy_main.cc
@@ -438,10 +438,6 @@ void ProxyMain::UpdateTopControlsState(TopControlsState constraints,
   channel_main_->UpdateTopControlsStateOnImpl(constraints, current, animate);
 }
 
-void ProxyMain::SetOutputIsSecure(bool output_is_secure) {
-  NOTREACHED() << "Only used by SingleProxyMain";
-}
-
 bool ProxyMain::SendCommitRequestToImplThreadIfNeeded(
     CommitPipelineStage required_stage) {
   DCHECK(IsMainThread());