Add SetSupportsQuic method to explicitly specify server that supports QUIC.

components/cronet/android/url_request_context_adapter.cc

Index: components/cronet/android/url_request_context_adapter.cc
diff --git a/components/cronet/android/url_request_context_adapter.cc b/components/cronet/android/url_request_context_adapter.cc
index 0feb0f13e4ad825768ca041f4665061cfcafeba8..305f0073ae0e40f5fbef997eee3d451b909745a9 100644
--- a/components/cronet/android/url_request_context_adapter.cc
+++ b/components/cronet/android/url_request_context_adapter.cc
@@ -13,7 +13,7 @@
 #include "net/cert/cert_verifier.h"
 #include "net/http/http_auth_handler_factory.h"
 #include "net/http/http_network_layer.h"
-#include "net/http/http_server_properties_impl.h"
+#include "net/http/http_server_properties.h"
 #include "net/proxy/proxy_config_service_fixed.h"
 #include "net/proxy/proxy_service.h"
 #include "net/ssl/ssl_config_service_defaults.h"
@@ -144,6 +144,11 @@ void URLRequestContextAdapter::InitializeURLRequestContext(
 
   context_.reset(context_builder.Build());
 
+  // Currently (circa M39) enabling QUIC requires setting probability threshold.
+  double quic_threshold = config->enable_quic ? 1.0f : 0.0f;
+  context_->http_server_properties()->SetAlternateProtocolProbabilityThreshold(
+      quic_threshold);
+
   if (VLOG_IS_ON(2)) {
     net_log_observer_.reset(new NetLogObserver());
     context_->net_log()->AddThreadSafeObserver(net_log_observer_.get(),
@@ -201,6 +206,19 @@ void URLRequestContextAdapter::StopNetLog() {
   }
 }
 
+void URLRequestContextAdapter::SetSupportsQuic(const net::HostPortPair& server,
+                                               uint16 alternate_port,
+                                               double probability) {
+  GetNetworkTaskRunner()->PostTask(
+      FROM_HERE,
+      base::Bind(&net::HttpServerProperties::SetAlternateProtocol,
+                 context_->http_server_properties(),
+                 server,
+                 alternate_port,
+                 net::AlternateProtocol::QUIC,
+                 probability));
+}
+
 void NetLogObserver::OnAddEntry(const net::NetLog::Entry& entry) {
   VLOG(2) << "Net log entry: type=" << entry.type()
           << ", source=" << entry.source().type << ", phase=" << entry.phase();