Currently, several non-consts are named as if they are const. The style
guide has a naming convention that fits these more accurately.

This CL changes the names to match the style guide.

Change-Id: Ib3425b76208e853b9049abe0e1be40e179124c57
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3472135Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Commit-Queue: Chris Blume <cblume@chromium.org>
Auto-Submit: Chris Blume <cblume@chromium.org>