Replace "nested message loop" with "nested run loop" in comments.

ui/aura/mus/window_tree_client.cc

Index: ui/aura/mus/window_tree_client.cc
diff --git a/ui/aura/mus/window_tree_client.cc b/ui/aura/mus/window_tree_client.cc
index 950bf1f8204a37ed0cd4ad573b30932c4480d8e3..4db2e071d2520b847efe398166b881de2cc5a802 100644
--- a/ui/aura/mus/window_tree_client.cc
+++ b/ui/aura/mus/window_tree_client.cc
@@ -108,8 +108,8 @@ class EventAckHandler : public base::RunLoop::NestingObserver {
 
   // base::RunLoop::NestingObserver:
   void OnBeginNestedRunLoop() override {
-    // Acknowledge the event immediately if a nested message loop starts.
-    // Otherwise we appear unresponsive for the life of the nested message loop.
+    // Acknowledge the event immediately if a nested run loop starts.
+    // Otherwise we appear unresponsive for the life of the nested run loop.
     if (ack_callback_) {
       ack_callback_->Run(ui::mojom::EventResult::HANDLED);
       ack_callback_.reset();