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

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index d2745b3148316620a4bde35bac99abf9b1ce5b5b..24fe62220253ebe4d0823378f8d3064f730cf266 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -103,6 +103,9 @@ const char kQuicFieldTrialName[] = "QUIC";
 const char kQuicFieldTrialEnabledGroupName[] = "Enabled";
 const char kQuicFieldTrialHttpsEnabledGroupName[] = "HttpsEnabled";
 
+const char kSpdyFieldTrialName[] = "SPDY";
+const char kSpdyFieldTrialDisabledGroupName[] = "SpdyDisabled";
+
 #if defined(OS_MACOSX) && !defined(OS_IOS)
 void ObserveKeychainEvents() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
@@ -711,6 +714,9 @@ void IOThread::InitializeNetworkOptions(const CommandLine& command_line) {
     if (command_line.HasSwitch(switches::kIgnoreUrlFetcherCertRequests))
       net::URLFetcher::SetIgnoreCertificateRequests(true);
 
+    std::string spdy_trial_group =
+        base::FieldTrialList::FindFullName(kSpdyFieldTrialName);
+
     if (command_line.HasSwitch(switches::kUseSpdy)) {

[Alexei Svitkine (slow), 2013/09/30 19:40:13]

Either add all of these flags to the config for the study, or call
FindFullName() only after you've checked all the flags that are not in the
config.

(Calling it marks the trial as "used" and therefore will be reported in
metrics.)

Alternatively, for flags that are not in the config, you can call Disable() on
the FieldTrial object returned by Find() to also disable reporting for that
trial.

[motek., 2013/09/30 20:44:29]

From the Department of Redundancy Department: pretty much what asvitkine@ wrote.


Do all these flags affect your experiment in any material way? If not, it might
be best to split the chain of ifs into a part affected by the study and the
rest. 

You may also want to single out the case where SPDY is disabled by policy and
FieldTrialList::Find()->Disable() it (not necessarily with this exact syntax
;-)).


On 2013/09/30 19:40:13, Alexei Svitkine wrote:

[ramant (doing other things), 2013/09/30 22:28:56]

Done.

[ramant (doing other things), 2013/09/30 22:28:56]

Done.

       std::string spdy_mode =
           command_line.GetSwitchValueASCII(switches::kUseSpdy);
@@ -726,8 +732,12 @@ void IOThread::InitializeNetworkOptions(const CommandLine& command_line) {
     } else if (command_line.HasSwitch(switches::kEnableNpnHttpOnly)) {
       net::HttpStreamFactory::EnableNpnHttpOnly();
     } else {
-      // Use SPDY/3.1 by default.
-      net::HttpStreamFactory::EnableNpnSpdy31();
+      if (spdy_trial_group == kSpdyFieldTrialDisabledGroupName) {
+         net::HttpStreamFactory::set_spdy_enabled(false);
+      } else {
+        // Use SPDY/3.1 by default.
+        net::HttpStreamFactory::EnableNpnSpdy31();
+      }
     }
   }