Added a field trial (finch experiment) to disable SPDY for x% of users.

chrome/browser/io_thread.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 "chrome/browser/io_thread.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 85 matching lines @@
 
 // The IOThread object must outlive any tasks posted to the IO thread before the
 // Quit task, so base::Bind() calls are not refcounted.
 
 namespace {
 
 const char kQuicFieldTrialName[] = "QUIC";
 const char kQuicFieldTrialEnabledGroupName[] = "Enabled";
 const char kQuicFieldTrialHttpsEnabledGroupName[] = "HttpsEnabled";
 
+const char kSpdyFieldTrialName[] = "SPDY";
+const char kSpdyFieldTrialDisabledGroupName[] = "Disabled";
+
 #if defined(OS_MACOSX) && !defined(OS_IOS)
 void ObserveKeychainEvents() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   net::CertDatabase::GetInstance()->SetMessageLoopForKeychainEvents();
 }
 #endif
 
 // Used for the "system" URLRequestContext.
 class SystemURLRequestContext : public net::URLRequestContext {
  public:
@@ skipping 603 matching lines @@
       net::HttpStreamFactory::EnableNpnHttp2Draft04();
     } else if (command_line.HasSwitch(switches::kEnableSpdy4a2)) {
       net::HttpStreamFactory::EnableNpnSpdy4a2();
     } else if (command_line.HasSwitch(switches::kDisableSpdy31)) {
       net::HttpStreamFactory::EnableNpnSpdy3();
     } else if (command_line.HasSwitch(switches::kEnableNpn)) {
       net::HttpStreamFactory::EnableNpnSpdy();
     } else if (command_line.HasSwitch(switches::kEnableNpnHttpOnly)) {
       net::HttpStreamFactory::EnableNpnHttpOnly();
     } else {
-      // Use SPDY/3.1 by default.
-      net::HttpStreamFactory::EnableNpnSpdy31();
+      std::string spdy_trial_group =
+          base::FieldTrialList::FindFullName(kSpdyFieldTrialName);

[Ryan Hamilton, 2013/09/28 13:58:40]

You need to make sure that you call FindFullName for every browser session, even
if it's disabled via command line flag.  You'll also need to add forcing flags
to the finch config.

You might want to ask the finch folks about what to do if spdy is disabled by
policy to make sure we account for that correctly.

[ramant (doing other things), 2013/09/29 23:41:32]

Done.
Will do.
CC'ed marcin finch advisor (will find from him about what to do if SPDY is
disabled via policy)

+      if (spdy_trial_group == kSpdyFieldTrialDisabledGroupName) {
+         net::HttpStreamFactory::set_spdy_enabled(false);
+      } else {
+        // Use SPDY/3.1 by default.
+        net::HttpStreamFactory::EnableNpnSpdy31();
+      }
     }
   }
 
   // TODO(rch): Make the client socket factory a per-network session
   // instance, constructed from a NetworkSession::Params, to allow us
   // to move this option to IOThread::Globals &
   // HttpNetworkSession::Params.
   if (command_line.HasSwitch(switches::kEnableTcpFastOpen))
     net::SetTCPFastOpenEnabled(true);
 }
@@ skipping 274 matching lines @@
   if (command_line.HasSwitch(switches::kDisableQuicHttps))
     return false;
 
   if (command_line.HasSwitch(switches::kEnableQuicHttps))
     return true;
 
   // HTTPS over QUIC should only be enabled if we are in the https
   // field trial group.
   return quic_trial_group == kQuicFieldTrialHttpsEnabledGroupName;
 }