chromeos: changes how DisplayManagerObservers are notified

services/ui/ws/user_display_manager.cc

Index: services/ui/ws/user_display_manager.cc
diff --git a/services/ui/ws/user_display_manager.cc b/services/ui/ws/user_display_manager.cc
index b32c5316764e8adc60eaad966dac01ed920aa8fc..f52663fbb4c1d4dc9f0b2ef080fd9e2bfb32a639 100644
--- a/services/ui/ws/user_display_manager.cc
+++ b/services/ui/ws/user_display_manager.cc
@@ -33,6 +33,18 @@ UserDisplayManager::UserDisplayManager(UserDisplayManagerDelegate* delegate,
 
 UserDisplayManager::~UserDisplayManager() {}
 
+void UserDisplayManager::DisableAutomaticNotification() {
+  DCHECK(notify_automatically_);
+  notify_automatically_ = false;
+}
+
+void UserDisplayManager::CallOnDisplaysChanged() {
+  display_manager_observers_.ForAllPtrs(
+      [this](mojom::DisplayManagerObserver* observer) {
+        CallOnDisplaysChanged(observer);
+      });
+}
+
 void UserDisplayManager::OnFrameDecorationValuesChanged() {
   got_valid_frame_decorations_ = true;
   CallOnDisplaysChangedIfNecessary();
@@ -100,13 +112,10 @@ bool UserDisplayManager::ShouldCallOnDisplaysChanged() const {
 }
 
 void UserDisplayManager::CallOnDisplaysChangedIfNecessary() {
-  if (!ShouldCallOnDisplaysChanged())
+  if (!notify_automatically_ || !ShouldCallOnDisplaysChanged())
     return;
 
-  display_manager_observers_.ForAllPtrs(
-      [this](mojom::DisplayManagerObserver* observer) {
-        CallOnDisplaysChanged(observer);
-      });
+  CallOnDisplaysChanged();
 }
 
 void UserDisplayManager::CallOnDisplaysChanged(