upload_symbols: Slow the upload rate.

We had a 200 ms minimum delay between upload attempts. Switch to 500ms
delay to avoid DoSing the crash server. Without deduping, and about 4000
symbols, this takes us from ~13 minutes wait time to ~33 minutes wait
time per upload. Or an increase of roughly 20 minutes.

BUG=chromium:610902
TEST=Unittest.

Change-Id: I03897a246a0fcbedfa31ec1a0bb60253ec5ebaf5
Previous-Reviewed-on: https://chromium-review.googlesource.com/358650
(cherry picked from commit 4559d4b74f22700116b08ccd2c0a72e6c6af1ed1)
Reviewed-on: https://chromium-review.googlesource.com/363064
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
1 file changed