Use SustainedQPS for --gitiles_qps flag.

The Golang rate limiter has a bucket of BURST, refilling at SUSTAINED
queries per second .

The googlesource.com rate limiter has a short-term QPS quota, and a
daily limit. The SUSTAINED better matches the short-term QPS quotum.

Change-Id: Id1c7ea5096ff0f623a21805f32f1c64454d6a1c7

gitiles/client.go

diff --git a/gitiles/client.go b/gitiles/client.go
index 36b4424..bd090f8 100644
--- a/gitiles/client.go
+++ b/gitiles/client.go
@@ -69,7 +69,7 @@
 	flag.StringVar(&defaultOptions.Address, "gitiles_url", "https://android.googlesource.com", "URL of the gitiles service.")
 	flag.StringVar(&defaultOptions.CookieJar, "gitiles_cookies", "", "path to cURL-style cookie jar file.")
 	flag.StringVar(&defaultOptions.UserAgent, "gitiles_agent", "slothfs", "gitiles User-Agent string to use.")
-	flag.IntVar(&defaultOptions.BurstQPS, "gitiles_qps", 4, "maximum Gitiles QPS")
+	flag.IntVar(&defaultOptions.SustainedQPS, "gitiles_qps", 4, "maximum Gitiles QPS")
 	return &defaultOptions
 }