[net/dns] Instrument DnsConfigService to measure performance and failures.

net/base/host_resolver_impl.cc

Index: net/base/host_resolver_impl.cc
diff --git a/net/base/host_resolver_impl.cc b/net/base/host_resolver_impl.cc
index edab00e1e87c2ad5244ca3244a1a1bd1687b3500..3f4d3b3831882ce2d339ae7588c7e0f226ab0552 100644
--- a/net/base/host_resolver_impl.cc
+++ b/net/base/host_resolver_impl.cc
@@ -1383,9 +1383,8 @@ class HostResolverImpl::Job : public PrioritizedDispatcher::Job {
       SetPortOnAddressList(requests_->front()->info().port(), &list);
       // Record this histogram here, when we know the system has a valid DNS
       // configuration.
-      UMA_HISTOGRAM_ENUMERATION("AsyncDNS.HaveDnsConfig",
-                                resolver_->received_dns_config_ ? 1 : 0,
-                                2);
+      UMA_HISTOGRAM_BOOLEAN("AsyncDNS.HaveDnsConfig",
+                            resolver_->received_dns_config_);
     }
 
     if ((net_error != ERR_ABORTED) &&