Don't log to debug.log unless debugging is on

[dadatuputi]

Description

On Windows, a file 'debug.log' file is opened in the user's Documents folder while Brave is open.

This is unexpected behavior - I don't expect the browser to ship with debugging enabled, and I don't expect a log file to be placed in such a conspicuous place as my Documents folder if I haven't explicitly enabled debug mode.

Thanks for looking into it.

Steps to Reproduce

1. Install Brave
2. Have loggable events/errors happen

Brave version (brave://version info)

Brave | 0.62.51 Chromium: 73.0.3683.103 (Official Build) (64-bit)
Revision | e82a658d8159cabbd4938c1660f9bb00b4a82a23-refs/branch-heads/3683@{#902}
OS | Windows 10 OS Build 17763.437