libdot: add helper script for crushing images
libdot: add helper script for crushing images

Add helper for crushing png & jpg images so we don't need to remember
how to do it.  We use the existing Chromium script for png files.

Change-Id: I7e6436a3a75e8bfdd8454d4e8ae548dfff282244
Reviewed-on: https://chromium-review.googlesource.com/1097619
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Vitaliy Shipitsyn <6f51537d61e46a00bf958b60dbef5b5870c2bf22@google.com>

chromium/hterm,chromium/hterm,chromium/hterm,chromium/hterm