Restrict Instant field trial to UMA opt-in users.

chrome/browser/instant/instant_field_trial.cc

Index: chrome/browser/instant/instant_field_trial.cc
diff --git a/chrome/browser/instant/instant_field_trial.cc b/chrome/browser/instant/instant_field_trial.cc
index 2c3e63d7e7fd65772eb47a3db1b0473b847655c3..54d4e75e46ee7e92595fd6ca1fd0d4280efbb92f 100644
--- a/chrome/browser/instant/instant_field_trial.cc
+++ b/chrome/browser/instant/instant_field_trial.cc
@@ -4,24 +4,37 @@
 
 #include "chrome/browser/instant/instant_field_trial.h"
 
+#include "base/metrics/field_trial.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/pref_names.h"
 
 namespace {
-bool field_trial_active_ = false;
+
+int kControlGroupId1 = 0;

[sky, 2011/08/08 16:10:54]

Add descriptions. Using kFoo implies these are constant, when they aren't
really.

[sreeram, 2011/08/08 16:30:10]

Done.

+int kControlGroupId2 = 0;
+int kExperimentGroupId1 = 0;
+int kExperimentGroupId2 = 0;
+
 }
 
 // static
 void InstantFieldTrial::Activate() {
-  field_trial_active_ = true;
+  scoped_refptr<base::FieldTrial> trial(
+      new base::FieldTrial("Instant", 10000, "InstantInactive", 2012, 1, 1));
+
+  if (!base::FieldTrialList::IsOneTimeRandomizationEnabled())
+    return;
+  trial->UseOneTimeRandomization();
+
+  kControlGroupId1 = trial->AppendGroup("InstantControl1", 4500);  // 45%
+  kControlGroupId2 = trial->AppendGroup("InstantControl2", 4500);  // 45%
+  kExperimentGroupId1 = trial->AppendGroup("InstantExperiment1", 500);  // 5%
+  kExperimentGroupId2 = trial->AppendGroup("InstantExperiment2", 500);  // 5%
 }
 
 // static
 InstantFieldTrial::Group InstantFieldTrial::GetGroup(Profile* profile) {
-  if (!field_trial_active_)
-    return INACTIVE;
-
   if (profile->IsOffTheRecord())
     return INACTIVE;
 
@@ -32,11 +45,24 @@ InstantFieldTrial::Group InstantFieldTrial::GetGroup(Profile* profile) {
     return INACTIVE;
   }
 
-  const int random = prefs->GetInteger(prefs::kInstantFieldTrialRandomDraw);
-  return random < 4500 ? CONTROL1 :    // 45%
-         random < 9000 ? CONTROL2 :    // 45%
-         random < 9500 ? EXPERIMENT1   //  5%
-                       : EXPERIMENT2;  //  5%
+  const int group = base::FieldTrialList::FindValue("Instant");
+
+  if (group == base::FieldTrial::kNotFinalized ||
+      group == base::FieldTrial::kDefaultGroupNumber) {
+    return INACTIVE;
+  }
+
+  if (group == kControlGroupId1) {

[sky, 2011/08/08 16:10:54]

no {}

[sreeram, 2011/08/08 16:30:10]

Done.

+    return CONTROL1;
+  } else if (group == kControlGroupId2) {
+    return CONTROL2;
+  } else if (group == kExperimentGroupId1) {
+    return EXPERIMENT1;
+  } else if (group == kExperimentGroupId2) {
+    return EXPERIMENT2;
+  } else {
+    return INACTIVE;
+  }
 }
 
 // static