Enable the simplified-fullscreen-ui flag by default on Aura.

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 f0858195ed0c5c837769894d614da882751f2345..edb4aa8007ac94e8010a2ccf00d203b48bd0a753 100644
--- a/chrome/browser/ui/exclusive_access/exclusive_access_manager.cc
+++ b/chrome/browser/ui/exclusive_access/exclusive_access_manager.cc
@@ -101,7 +101,12 @@ bool ExclusiveAccessManager::IsSimplifiedFullscreenUIEnabled() {
     return false;
   }
 
+  // Enabled by default on Aura platforms only.
+#if defined(USE_AURA)
+  return true;
+#else
   return false;
+#endif  // defined(USE_AURA)
 }
 
 void ExclusiveAccessManager::OnTabDeactivated(WebContents* web_contents) {