Refer to Bug 1269953 # Test Case 1. Launch the browser with blank page 2. Input the google doc url with 1 pages table content https://goo.gl/ASWnsK 3. Select all objects 4. Delete all objects 5. Close the browser # Try to identify the time for the action "Delete All". profilerMark_4() is for the action "Delete All": 50305 - 50021 = 284 ms Profiler: https://goo.gl/mDDYKj From Gecko Profiling data, the Range [50001, 50315]: 313 100.0% Startup::XRE_Main 177 56.5% ├─ nsViewManager::DispatchEvent 177 56.5% │ └─ EventDispatcher::Dispatch │ └─ ...so on └─ ...so on