Test Case 1. Launch the browser with blank page 2. Input the google doc url with 1 table content https://goo.gl/W1txdG 3. Close the browser Profiler: https://goo.gl/1rehgy From Perf Timing json, the "domLoading" to "loadEventEnd" are 424 ~ 7882 ms, diff is 7458 ms. Switch to profiling data, we can only check the Add-on start/end mark. The first "Start" to last "End" marks, time-stamp are 33189 ~ 41375 ms, diff is 8186 ms. From Gecko Profiling data, the Range [33105, 41343]: 8111 100.0% Startup::XRE_Main 2337 32.4% ├─ nsHtml5TreeOpExecutor::RunFlushLoop 2168 26.7% │ ├─ nsJSUtils::EvaluateString 137 1.7% │ ├─ EventDispatcher::Dispatch │ └─ ...so on │ 1800 22.2% ├─ nsInputStreamPump::OnInputStreamReady 1650 20.3% │ ├─ nsInputStreamPump::OnStateStop 106 1.3% │ ├─ nsInputStreamPump::OnStateStart 44 0.5% │ └─ nsInputStreamPump::OnStateTransfer │ 1127 13.9% ├─ Timer::Fire 1102 13.6% │ ├─ js::RunScript 14 0.2% │ ├─ nsCycleCollector::forgetSkippable │ └─ ...so on │ 624 7.7% ├─ nsRefreshDriver::Tick 323 4.0% │ ├─ PressShell::Paint 113 1.4% │ ├─ PressShell::Flush (Flush_Style) │ └─ ...so on └─ ...so on Firefox version: 45.0.2 OS version: Ubuntu 14.04 LTS 64-bit