Gather chrome.PREVIOUS log when collecting feedback report

We already grab the chrome log, and also grabbing the PREVIOUS log will
help with diagnosing Chrome crashes.

Bug: 979897
Test: Manually verified in feedback report
Change-Id: If2be64ca0106097dda4693f24dac6f2e50a92e62
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1704033
Auto-Submit: Jeffrey Kardatzke <jkardatzke@google.com>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Jeffrey Kardatzke <jkardatzke@google.com>
Cr-Commit-Position: refs/heads/master@{#678436}

chrome/browser/chromeos/system_logs/OWNERS

 afakhry@chromium.org
+jkardatzke@chromium.org
 
 # COMPONENT: Platform>Apps>Feedback

chrome/browser/chromeos/system_logs/debug_daemon_log_source.cc

@@ -42,6 +42,7 @@ constexpr struct UserLogs {
   const char* log_file_relative_path;
 } kUserLogs[] = {
     {"chrome_user_log", "log/chrome"},
+    {"chrome_user_log.PREVIOUS", "log/chrome.PREVIOUS"},
     {"libassistant_user_log", "log/libassistant.log"},
     {"login-times", "login-times"},
     {"logout-times", "logout-times"},