upload_symbols: Update CRASH_SERVER_FILE_LIMIT

The symbol file size limit on the crash server was changed from 350MB to
500MB.

BUG=b:30860471
BUG=b:31287021
BUG=chromium:645351
TEST=./scripts/upload_symbols_unittest

Change-Id: I9fbb306f8f055cd61c9cff54ce2581ae75a71fc5
Reviewed-on: https://chromium-review.googlesource.com/381697
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Ryo Hashimoto <hashimoto@chromium.org>
Commit-Queue: Ryo Hashimoto <hashimoto@chromium.org>
(cherry picked from commit f66d8ca8611628372f6ccd685a95144452cb2b93)
Reviewed-on: https://chromium-review.googlesource.com/384073
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
2 files changed