Fix use after free for cached_displays_.

ui/display/manager/chromeos/display_configurator.cc

Index: ui/display/manager/chromeos/display_configurator.cc
diff --git a/ui/display/manager/chromeos/display_configurator.cc b/ui/display/manager/chromeos/display_configurator.cc
index 8258d23d29eaddcb40e5c3807cd4e73e448b1dce..39a3f6ef751fce0efe4dc1e4acbb0584f6ec7617 100644
--- a/ui/display/manager/chromeos/display_configurator.cc
+++ b/ui/display/manager/chromeos/display_configurator.cc
@@ -524,10 +524,10 @@ void DisplayConfigurator::Init(
 
   // If the delegate is already initialized don't update it (For example, tests
   // set their own delegates).
-  if (!native_display_delegate_) {
+  if (!native_display_delegate_)
     native_display_delegate_ = std::move(display_delegate);
-    native_display_delegate_->AddObserver(this);
-  }
+
+  native_display_delegate_->AddObserver(this);
 }
 
 void DisplayConfigurator::TakeControl(const DisplayControlCallback& callback) {
@@ -947,6 +947,11 @@ void DisplayConfigurator::OnConfigurationChanged() {
                          this, &DisplayConfigurator::ConfigureDisplays);
 }
 
+void DisplayConfigurator::OnDisplaySnapshotsInvalidated() {
+  VLOG(1) << "Display snapshots invalidated.";
+  cached_displays_.clear();
+}
+
 void DisplayConfigurator::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }