Fix bug in ALTERNATE_PROTOCOL_USAGE_MAPPING_MISSING histogram

net/http/http_server_properties_impl.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/http/http_server_properties_impl.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 265 matching lines @@
                    << server.ToString()
                    << " from [Port: " << existing_alternate.port
                    << ", Protocol: " << existing_alternate.protocol
                    << ", Probability: " << existing_alternate.probability
                    << "] to [Port: " << alternate_port
                    << ", Protocol: " << alternate_protocol
                    << ", Probability: " << alternate_probability
                    << "].";
     }
   } else {
-    // TODO(rch): Consider the case where multiple requests are started
-    // before the first completes. In this case, only one of the jobs
-    // would reach this code, whereas all of them should should have.
-    HistogramAlternateProtocolUsage(ALTERNATE_PROTOCOL_USAGE_MAPPING_MISSING,
-                                    alternate_protocol_experiment_);
+    if (alternate_probability >= alternate_protocol_probability_threshold_) {
+      // TODO(rch): Consider the case where multiple requests are started
+      // before the first completes. In this case, only one of the jobs
+      // would reach this code, whereas all of them should should have.
+      HistogramAlternateProtocolUsage(ALTERNATE_PROTOCOL_USAGE_MAPPING_MISSING,
+                                      alternate_protocol_experiment_);
+    }
   }
 
   alternate_protocol_map_.Put(server, alternate);
 
   // If this host ends with a canonical suffix, then set it as the
   // canonical host.
   for (size_t i = 0; i < canoncial_suffixes_.size(); ++i) {
     std::string canonical_suffix = canoncial_suffixes_[i];
     if (EndsWith(server.host(), canoncial_suffixes_[i], false)) {
       HostPortPair canonical_host(canonical_suffix, server.port());
@@ skipping 210 matching lines @@
   base::TimeDelta delay = when > now ? when - now : base::TimeDelta();
   base::MessageLoop::current()->PostDelayedTask(
       FROM_HERE,
       base::Bind(
           &HttpServerPropertiesImpl::ExpireBrokenAlternateProtocolMappings,
           weak_ptr_factory_.GetWeakPtr()),
       delay);
 }
 
 }  // namespace net