Replace old resources download script with depot_tools

With help from hinoka@, we're now using a more efficient approach
to download only the files that have changed from Google Storge.

When uploading new resource files, use
upload_to_google_storage.py --bucket chromium-webrtc-resources ./filename
which of course requires gsutil authentication setup.

NOTICE: Before deploying this, svn:ignore should be removed for
the resources folder, or the bots will run into problems with a
non-versioned file being found in the checkout during sync (as
this CL adds resources to version control).

All developers will also need to be informed to wipe their local
resources dir to avoid getting an error during checkout due to the
already existing non-versioned resources directory.

BUG=2294
TEST=locally running gclient runhooks
R=andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2095004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5076 4adac7df-926f-26a2-2b94-8c16560cd09d
123 files changed