DEPS: Add Android tombstone resolution dependencies. Add third_party/android_platform and tools/python from the Chromium git to satisfy dependencies for the build/android/tombstones.py script. Bug: angleproject:5933 Change-Id: Ie19eec46c8cab208cde5064118ae655303e12fa7 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2878848 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Lubosz Sarnecki <lubosz.sarnecki@collabora.com>