[Bug 2048792] [NEW] Firefox utilizins 100% of station CPU

[Steve Smaldone]

Public bug reported:

At a high level, in certain instances we’re experiencing sustained
abnormally high (100%) CPU utilization from Firefox.  This utilization
is competing with other critical application processes on the systems,
starving them of resources, causing issues in the application
processing.  This happens, at times, when the browser should be idle,
even.

We have not isolated this issue to be a bug with firefox itself or an issue with the webpage content being provided to the browser. Regardless, here are the symptoms:
    * CPU usage is extremely high for the FireFox process (>100% on average vs <10% average for healthy stations) even while the screen is sitting idle (no animations, user interactions, etc.)
   * We have isolated the thread within FireFox causing the most CPU usage to the Renderer thread with the SwComposite threads also consuming abnormally high CPU.
   * In the FireFox Task and Process Managers, we have validated there is no single tab or window consuming abnormally high CPU, just the FireFox master process.
   * Additionally, we have confirmed that the FireFox browser history (taken from the places.sqlite file) does not have any webpages being loaded during the times when CPU consumption experiences a step function change up or down.
   * We also have linux perf logs for the FireFox process on healthy stations and impacted stations while sitting idle on the login screen, which can provide some stack traces for the Renderer and other threads which may be more useful to someone with FireFox expertise.
   * The biggest difference is that the impacted workcells have the Renderer and Compositor 'tracks' very active while the healthy workcells see no usage of these tracks at all.
   * These 2 tracks also have supporting tracks such as SwComposite and WRRendererBackend#X. There were 2 of each of these, which may indicate the issue is happening across both FireFox windows. For reference, the stations always have 2 windows open: one for the screen UI and one for the projector on the pod face.
   * (Using the term 'track' here as defined by the open source FireFox profiler: https://profiler.firefox.com/. Basically a thread within the FireFox main process) 
   * There are many memory copy and SW interrupt calls being made in these tracks.
   * This validates that FireFox is contributing to increased software interrupt load
   * Additionally, we found an interesting pair of calls occurring periodically in the Renderer track. We have not deep dived these yet, but on the off chance it matters, we're including it in this report:
   * viaduct_log_error - every 50 - 500ms
   * wgpu_render_pass_end_pipeline_statistics_query - every 50 - 1000ms

** Affects: firefox (Ubuntu)
     Importance: Undecided
         Status: New

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Title:
  Firefox utilizins 100% of station CPU

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