Use Histogram algorithm to calculate DNS timeout. Honor DnsConfig timeout if it exceeds 5s.

net/dns/dns_session_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/dns/dns_session.h"
 
 #include <list>
 
 #include "base/bind.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 202 matching lines @@
 
   lease1.reset();
   EXPECT_TRUE(DidFree(0));
   EXPECT_TRUE(NoMoreEvents());
 
   lease2.reset();
   EXPECT_TRUE(DidFree(1));
   EXPECT_TRUE(NoMoreEvents());
 }
 
-} // namespace
+// Expect default calculated timeout to be within 10ms of in DnsConfig.
+TEST_F(DnsSessionTest, HistogramTimeoutNormal) {
+  Initialize(2);
+  base::TimeDelta timeoutDelta = session_->NextTimeout(0, 0) - config_.timeout;
+  EXPECT_LT(timeoutDelta.InMilliseconds(), 10);
+}
+
+// Expect short calculated timeout to be within 10ms of in DnsConfig.
+TEST_F(DnsSessionTest, HistogramTimeoutShort) {
+  config_.timeout = base::TimeDelta::FromMilliseconds(15);
+  Initialize(2);
+  base::TimeDelta timeoutDelta = session_->NextTimeout(0, 0) - config_.timeout;
+  EXPECT_LT(timeoutDelta.InMilliseconds(), 10);
+}
+
+// Expect long calculated timeout to be equal to one in DnsConfig.
+TEST_F(DnsSessionTest, HistogramTimeoutLong) {
+  config_.timeout = base::TimeDelta::FromSeconds(15);
+  Initialize(2);
+  base::TimeDelta timeout = session_->NextTimeout(0, 0);
+  EXPECT_EQ(config_.timeout.InMilliseconds(), timeout.InMilliseconds());
+}
+
+}  // namespace
 
 } // namespace net