Add a new field trial for Instant.

chrome/browser/instant/instant_field_trial.h

Index: chrome/browser/instant/instant_field_trial.h
diff --git a/chrome/browser/instant/instant_field_trial.h b/chrome/browser/instant/instant_field_trial.h
index 53560663d156775cf17236e2ff0ea2130b1d85d0..38fb7463e43bbdae783a632726d045da2240ca44 100644
--- a/chrome/browser/instant/instant_field_trial.h
+++ b/chrome/browser/instant/instant_field_trial.h
@@ -19,19 +19,25 @@ class Profile;
 // Instant preference is respected. Incognito profiles are also INACTIVE.
 //
 // The following mutually exclusive groups each select a small random sample of
-// the remaining users:
+// the remaining users. Instant is enabled with preloading for the EXPERIMENT
+// groups. It remains disabled, as is default, for the CONTROL groups.
 //
-// INSTANT_EXPERIMENT: Instant is enabled, but only for search. Instant is also
-//     preloaded. If the user hasn't opted to send metrics (UMA) data, they are
+// INSTANT_EXPERIMENT: Queries are issued as the user types, and previews are
+//     shown. If the user hasn't opted to send metrics (UMA) data, they are
 //     bounced back to INACTIVE.
 //
-// INSTANT_CONTROL: Instant remains disabled, as is default. If the user hasn't
-//     opted to send metrics (UMA) data, they are bounced back to INACTIVE.
+// HIDDEN_EXPERIMENT: Queries are issued as the user types, but no preview is
+//     shown until they press <Enter>. If the user hasn't opted to send metrics
+//     (UMA) data, they are bounced back to INACTIVE.
 //
-// HIDDEN_EXPERIMENT: Instant is enabled in "search only" mode, but queries are
-//     issued only when the user presses <Enter>. No previews are shown.
+// SILENT_EXPERIMENT: No queries are issued until the user presses <Enter>. No

[sky, 2011/10/24 15:03:31]

How about HIDDEN_UNTIL_COMMIT?

[sreeram, 2011/10/24 17:14:50]

I prefer SILENT. The other field trial is also "hidden until commit" (i.e., the
preview_contents is not shown until commit). The difference is that this
experiment doesn't send any queries over the wire, which I think is captured
well by the name "SILENT".

+//     previews are shown. The user is not required to send metrics (UMA) data.
 //
-// HIDDEN_CONTROL: Instant remains disabled, as is default.
+// UMA_CONTROL: Instant is disabled. If the user hasn't opted to send metrics
+//     (UMA) data, they are bounced back to INACTIVE.
+//
+// ALL_CONTROL: Instant is disabled. The user is not required to send metrics
+//     (UMA) data.
 //
 // Users not chosen into any of the above groups are INACTIVE.
 //
@@ -43,15 +49,17 @@ class InstantFieldTrial {
   enum Group {
     INACTIVE,
 
-    INSTANT_CONTROL_A,
-    INSTANT_CONTROL_B,
     INSTANT_EXPERIMENT_A,
     INSTANT_EXPERIMENT_B,
-
-    HIDDEN_CONTROL_A,
-    HIDDEN_CONTROL_B,
     HIDDEN_EXPERIMENT_A,
     HIDDEN_EXPERIMENT_B,
+    SILENT_EXPERIMENT_A,
+    SILENT_EXPERIMENT_B,
+
+    UMA_CONTROL_A,
+    UMA_CONTROL_B,
+    ALL_CONTROL_A,
+    ALL_CONTROL_B,
   };
 
   // Activate the field trial. Before this call, all calls to GetGroup will
@@ -64,12 +72,12 @@ class InstantFieldTrial {
   // Check if the user is in one of the EXPERIMENT groups.
   static bool IsExperimentGroup(Profile* profile);
 
-  // Check if the user is in the INSTANT_EXPERIMENT group.
-  static bool IsInstantExperiment(Profile* profile);
-
   // Check if the user is in the HIDDEN_EXPERIMENT group.
   static bool IsHiddenExperiment(Profile* profile);
 
+  // Check if the user is in the SILENT EXPERIMENT group.
+  static bool IsSilentExperiment(Profile* profile);
+
   // Returns a string describing the user's group. Can be added to histogram
   // names, to split histograms by field trial groups.
   static std::string GetGroupName(Profile* profile);