3.3.4 - Refactoring, optimizations, dependencies, docs

Refactoring, optimizations, dependencies, docs

• Refactoring
• Perform Firefox optimizations
• Disable 3D APIs in Chromium to speed up WebGL sites
  --> This resolves #1384
• Refresh Python dependencies , Refresh a Python dependency
  --> requests, chardet, charset-normalizer, and cffi
• Improve help docs for the "--variables" option

--variables=DICT
A var dict to pass to tests from the command line.

Example usage:  (with pytest)
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Option: --variables='{"special":123}'
Access: self.variables["special"]  # (123)
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Option: --variables='{"color":"red","num":42}'
Access: self.variables["color"]  # ("red")
Access: self.variables["num"]  # (42)
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