1127858 - Bad framerate and high CPU when context menu is open, window out of focus or hovering some overlays (non-MSE HTML5 WebM)

Status: RESOLVED INCOMPLETE

(Core Graveyard :: Plug-ins, defect)

Description

[[SV Manager] Florin Mezei, QA (:FlorinMezei)]

Reproducible with: 
- Firefox 36 Beta 5 - BuildID: 20150129200438

Reproducible on: Windows XP x86
NOT reproducible on: Windows XP x64, Vista x86, Vista x64 

Steps to reproduce:
1. Open Firefox with a clean profile and go to any youtube video (e.g. https://www.youtube.com/watch?v=c86t8hoVw8E).
2. Open the task manager to see how much CPU Firefox takes (5-10% in my case).
3. Try the following actions while video is playing: 
a) Right click outside of the video area to bring up the context menu
b) Open "Stats for nerds" and hover the "x" button
c) Hover video overlays
d) bring another window to the foreground

Expected results:
Actions from step #3 do not affect the video frame rate or CPU usage.

Actual results:
All actions from step #3 cause a very visible drop in frame rate and CPU usage climbs to around 35% each time. Dismissing the actions from step #3 causes the frame rate and CPU usage to recover. See http://www.screencast.com/t/z6oG4AnGNqB.

Notes:
- Windows XP x86 seems to be the only one affected. Any other Windows version (tried XP and Vista for now) on the same machine works fine in this scenario
- Video card is: AMD Radeon HD 3000
- in order to check this on Vista, I've set "media.mediasource.enabled"=false
- the issue is not much unlike what I see with Firefox 35.0.1 on the same machine with XP x86. This uses Flash, but I get the same loss in frame rate and high CPU usage when performing actions from step #3.

Comment 1

[Anthony Jones (:ajones, :kentuckyfriedtakahe, :k17e)]

XP -> Flash issue

Comment 2

[Benjamin Smedberg]

Resolving old bugs which are likely not relevant any more, since NPAPI plugins are deprecated.