Make the default alternate protcol probability threshold 1, not 0.

This means that by default, Chrome will honor headers like:
  Alternate-Protocol: 80:quic
  Alternate-Protocol: 80:quic,p=1
But not:
  Alternate-Protocol: 80:quic,p=.5
Eventually we need to switch to a dynamic threshold, but on step at a time.

Review URL: https://codereview.chromium.org/411423003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285473 0039d316-1c4b-4281-b951-d872f2087c98

net/http/http_network_session.cc

@@ -81,7 +81,7 @@ HttpNetworkSession::Params::Params()
       force_spdy_over_ssl(true),
       force_spdy_always(false),
       use_alternate_protocols(false),
-      alternate_protocol_probability_threshold(0),
+      alternate_protocol_probability_threshold(1),
       enable_websocket_over_spdy(false),
       enable_quic(false),
       enable_quic_port_selection(true),

net/http/http_server_properties_impl.cc

@@ -26,7 +26,7 @@ HttpServerPropertiesImpl::HttpServerPropertiesImpl()
       alternate_protocol_experiment_(
           ALTERNATE_PROTOCOL_NOT_PART_OF_EXPERIMENT),
       spdy_settings_map_(SpdySettingsMap::NO_AUTO_EVICT),
-      alternate_protocol_probability_threshold_(0),
+      alternate_protocol_probability_threshold_(1),
       weak_ptr_factory_(this) {
   canoncial_suffixes_.push_back(".c.youtube.com");
   canoncial_suffixes_.push_back(".googlevideo.com");
@@ -198,7 +198,7 @@ bool HttpServerPropertiesImpl::HasAlternateProtocol(
     return true;
   AlternateProtocolMap::const_iterator it = alternate_protocol_map_.Get(server);
   if (it != alternate_protocol_map_.end() &&
-      it->second.probability > alternate_protocol_probability_threshold_) {
+      it->second.probability >= alternate_protocol_probability_threshold_) {
     return true;
   }
 

net/http/http_server_properties_impl_unittest.cc

@@ -254,6 +254,13 @@ TEST_F(AlternateProtocolServerPropertiesTest, Basic) {
   EXPECT_FALSE(impl_.HasAlternateProtocol(test_host_port_pair));
 }
 
+TEST_F(AlternateProtocolServerPropertiesTest, DefaultProbabilityExcluded) {
+  HostPortPair test_host_port_pair("foo", 80);
+  impl_.SetAlternateProtocol(test_host_port_pair, 443, NPN_SPDY_3, .99);
+
+  EXPECT_FALSE(impl_.HasAlternateProtocol(test_host_port_pair));
+}
+
 TEST_F(AlternateProtocolServerPropertiesTest, Probability) {
   impl_.SetAlternateProtocolProbabilityThreshold(.25);