Enable gathering and sending system logs for Desktop Chrome.
Currently the system log gathering code is only limited to ChromeOS. Move the code out of ChromeOS so it can be used by regular Chrome.
The code has been refactored to leave the ChromeOS specific logs gathering code under the c/b/chromeos directory while moving the general system logs code under the c/b/feedback directory. We didn't move system_logs directory under c/b/ since system logs are mostly related with feedback and to keep the c/b/ clutter low.

Individual developers can add their own additional logs for Chrome under c/b/feedback/system_logs/log_sources following the *_log_source.* templates already there.

R=asargent@chromium.org, xiyuan@chromium.org
BUG=306532

Review URL: https://codereview.chromium.org/105873004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241477 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241477