Audit requestAnimationFrame() and possible timing attacks

We should investigate how effective timing attacks are against Tor Browser if we time the rendering process with requestAnimationFrame().

Some examples to study are mentioned in:

https://dl.acm.org/citation.cfm?id=2516712 http://www.contextis.com/files/Browser_Timing_Attacks.pdf

Ideally, the audit would contain suggestions on how to mitigate possible issues.