Change MISSING_VIA_HEADER_4XX bypasses to only last 1 second.

components/data_reduction_proxy/common/data_reduction_proxy_headers.cc

Index: components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
diff --git a/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc b/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
index 377db65cbb228d924b241c2c6b15780dd829dd84..c8a11f9a48efd1904fcd9863ffe5b464f6855847 100644
--- a/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
+++ b/components/data_reduction_proxy/common/data_reduction_proxy_headers.cc
@@ -240,6 +240,12 @@ DataReductionProxyBypassType GetDataReductionProxyBypassType(
     // Separate this case from other responses that are missing the header.
     if (headers->response_code() >= net::HTTP_BAD_REQUEST &&
         headers->response_code() < net::HTTP_INTERNAL_SERVER_ERROR) {
+      // At this point, any 4xx response that is missing the via header
+      // indicates an issue that is scoped to only the current request, so only
+      // bypass the data reduction proxy for a second.
+      // TODO(sclittle): Change this to only bypass the current request once
+      // that is fully supported, see http://crbug.com/418342.
+      data_reduction_proxy_info->bypass_duration = TimeDelta::FromSeconds(1);

[bengr, 2014/10/10 21:52:50]

There should be a test for this somewhere, either in headers_unittest or
protocol_unittest. If this case isn't covered, please add it.

[sclittle, 2014/10/10 22:02:08]

Done.

       return BYPASS_EVENT_TYPE_MISSING_VIA_HEADER_4XX;
     }
     return BYPASS_EVENT_TYPE_MISSING_VIA_HEADER_OTHER;