Context: https://crrev.com/c/660978

With Blink C++ style merging with Chromium style, and with the code move to third_party/blink, it's probably also a good time to get rid of the Blink-specific style rules for Python.

As noted in: https://www.chromium.org/blink/coding-style

[Blink Python style] differs from Chromium coding style in three respects:
 - line length limit is larger (132 chars, unlike PEP-8)
 - uses 4 space indent (like PEP-8)
 - uses function_name, method_name rather than FunctionName, MethodName (like PEP-8).

As a compromise, we could potentially switch to 80-column width and 2-space indent, but allow a mix of snake_case and CamelCase.

Note about reformatting: While autopep8 (used by format-webkitpy) gets us most of the way there, it doesn't do comment text re-flow and doesn't handle all long line reformatting. It might be convenient use another tool like yapf for the cases that autopep8 doesn't handle.