Remove the simplified-fullscreen-ui flag on Mac.

chrome/browser/ui/exclusive_access/exclusive_access_manager.cc

Index: chrome/browser/ui/exclusive_access/exclusive_access_manager.cc
diff --git a/chrome/browser/ui/exclusive_access/exclusive_access_manager.cc b/chrome/browser/ui/exclusive_access/exclusive_access_manager.cc
index 3492dc448f0195afd22ddf435be1e4ec709c5552..d186bcc65b5afba6f080c5b648efa1060f1673a7 100644
--- a/chrome/browser/ui/exclusive_access/exclusive_access_manager.cc
+++ b/chrome/browser/ui/exclusive_access/exclusive_access_manager.cc
@@ -108,7 +108,13 @@ bool ExclusiveAccessManager::IsExperimentalKeyboardLockUIEnabled() {
 
 // static
 bool ExclusiveAccessManager::IsSimplifiedFullscreenUIEnabled() {
+#if defined(OS_MACOSX)
+  // Always enabled on Mac (the mouse cursor tracking required to implement the
+  // non-simplified version is not implemented).
+  return true;
+#else
   return base::FeatureList::IsEnabled(features::kSimplifiedFullscreenUI);
+#endif
 }
 
 void ExclusiveAccessManager::OnTabDeactivated(WebContents* web_contents) {