Add Alternative Service field trial.

Before this CL:
 * If "use_alternative_service" QUIC trial param was set, both same host and
   different host Alt-Svc headers were parsed and used.  If this param was not
   set, no Alt-Svc headers were parsed, and in-memory entries (from
   Alternate-protocol headers or loaded from disk) were only used if they
   referred to the same host.

After this CL:
 * AltSvc field trial controls whether Alt-Svc headers are parsed.
 * "enable_alternative_service_with_different_host" QUIC trial param control
   whether in-memory Alt-Svc entries with different host (parsed in current
   session or loaded from disk) are used.

Default values are not changed by this CL.

This CL allows testing of same-host Alt-Svc header behavior.  If no issues are
encountered, parsing Alt-Svc headers and using same-host entries can be enabled
by default, and Alternate-Protocols removed.

BUG=581331

Review URL: https://codereview.chromium.org/1639913002

Cr-Commit-Position: refs/heads/master@{#372348}

1 files changed, 9 insertions, 3 deletions

diff --git a/ios/chrome/browser/ios_chrome_io_thread.h b/ios/chrome/browser/ios_chrome_io_thread.h
index 432e9f4..5f0956f 100644
--- a/ios/chrome/browser/ios_chrome_io_thread.h
+++ b/ios/chrome/browser/ios_chrome_io_thread.h
@@ -140,7 +140,8 @@ class IOSChromeIOThread : public web::WebThreadDelegate {
     Optional<bool> enable_spdy_ping_based_connection_checking;
     net::NextProtoVector next_protos;
     std::set<net::HostPortPair> forced_spdy_exclusions;
-    Optional<bool> use_alternative_services;
+    Optional<bool> parse_alternative_services;
+    Optional<bool> enable_alternative_service_with_different_host;
     Optional<double> alternative_service_probability_threshold;
 
     Optional<bool> enable_npn;
@@ -230,6 +231,11 @@ class IOSChromeIOThread : public web::WebThreadDelegate {
                                    const VariationParameters& quic_trial_params,
                                    Globals* globals);
 
+  // Configures Alternative Services in |globals| based on the field trial
+  // group.
+  static void ConfigureAltSvcGlobals(base::StringPiece altsvc_trial_group,
+                                     IOSChromeIOThread::Globals* globals);
+
   // Configures NPN in |globals| based on the field trial group.
   static void ConfigureNPNGlobals(base::StringPiece npn_trial_group,
                                   Globals* globals);
@@ -299,8 +305,8 @@ class IOSChromeIOThread : public web::WebThreadDelegate {
   // Returns true if QUIC should prefer AES-GCN even without hardware support.
   static bool ShouldQuicPreferAes(const VariationParameters& quic_trial_params);
 
-  // Returns true if QUIC should enable alternative services.
-  static bool ShouldQuicEnableAlternativeServices(
+  // Returns true if QUIC should enable alternative services for different host.
+  static bool ShouldQuicEnableAlternativeServicesForDifferentHost(
       const VariationParameters& quic_trial_params);
 
   // Returns the maximum number of QUIC connections with high packet loss in a