Less attempted magic in pulling toolchain
Less attempted magic in pulling toolchain

- Don't try to wrap download_from_google_storage --config, instead just
request that the user runs it manually. (This is annoying either way
but making it magically run makes it less clear what's going on, and so
harder to debug when something goes wrong, per linked bug).

- Check that SHA1s are passed as expected on the command line in case
the script is run directly, rather than from gyp_chromium.

R=scherkus@chromium.org
BUG=349596

Review URL: https://codereview.chromium.org/189093017

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@256049 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

svn2github/chromium-depot-tools,svn2github/chromium-depot-tools,svn2github/chromium-depot-tools