Use an experiment value to set the instant_extended.enabled pref default.

chrome/browser/ui/search/search.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/ui/search/search.h"
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/string_number_conversions.h"
 #include "base/string_split.h"
@@ skipping 15 matching lines @@
 // us maximum flexability in running experiments.
 // Field trials should be named things like "Group7 espv:2 themes:0".
 // The first token is always GroupN for some integer N, followed by a
 // space-delimited list of key:value pairs which correspond to these flags:
 const char kEnableOnThemesFlagName[] = "themes";
 const bool kEnableOnThemesDefault = false;
 
 const char kEmbeddedPageVersionFlagName[] = "espv";
 const int kEmbeddedPageVersionDefault = 1;
 
+const char kInstantExtendedActivationName[] = "instant";
+const chrome::search::InstantExtendedDefault kInstantExtendedActivationDefault =
+    chrome::search::INSTANT_USE_EXISTING;
+
 // Constants for the field trial name and group prefix.
 const char kInstantExtendedFieldTrialName[] = "InstantExtended";
 const char kGroupNumberPrefix[] = "Group";
 
 // If the field trial's group name ends with this string its configuration will
 // be ignored and Instant Extended will not be enabled by default.
 const char kDisablingSuffix[] = "DISABLED";
 
 }  // namespace
 
 namespace chrome {
 namespace search {
 
+InstantExtendedDefault InstantExtendedDefaultFromInt64(int64 default_value) {
+  switch (default_value) {
+    case 0: return INSTANT_FORCE_ON;
+    case 1: return INSTANT_USE_EXISTING;
+    case 2: return INSTANT_FORCE_OFF;
+    default: return INSTANT_USE_EXISTING;
+  }
+}
+
+InstantExtendedDefault GetInstantExtendedDefaultSetting() {
+  InstantExtendedDefault default_setting = INSTANT_USE_EXISTING;
+
+  FieldTrialFlags flags;
+  if (GetFieldTrialInfo(
+          base::FieldTrialList::FindFullName(kInstantExtendedFieldTrialName),
+          &flags, NULL)) {
+    uint64 trial_default = GetUInt64ValueForFlagWithDefault(
+        kInstantExtendedActivationName,
+        kInstantExtendedActivationDefault,
+        flags);
+    default_setting = InstantExtendedDefaultFromInt64(trial_default);
+  }
+
+  return default_setting;
+}
+
 // Check whether or not the Extended API should be used on the given profile.
 bool IsInstantExtendedAPIEnabled(Profile* profile) {
   return EmbeddedSearchPageVersion(profile) != 0;
 }
 
 // Determine what embedded search page version to request from the user's
 // default search provider.  If 0, the embedded search UI should not be enabled.
 // Note that the profile object here isn't const because we need to determine
 // whether or not the user has a theme installed as part of this check, and
 // that logic requires a non-const profile for whatever reason.
 uint64 EmbeddedSearchPageVersion(Profile* profile) {
   // Incognito windows do not currently use the embedded search API.
   if (!profile || profile->IsOffTheRecord())
     return 0;
 
   // Check Finch field trials.
   FieldTrialFlags flags;
-  uint64 group_number = 0;
-  base::FieldTrial* trial =
-      base::FieldTrialList::Find(kInstantExtendedFieldTrialName);
-  if (trial) {
-    std::string group_name = trial->group_name();
-    GetFieldTrialInfo(group_name, &flags, &group_number);
-  }
-
-  if (group_number > 0) {
+  if (GetFieldTrialInfo(
+          base::FieldTrialList::FindFullName(kInstantExtendedFieldTrialName),
+          &flags, NULL)) {
     uint64 espv = GetUInt64ValueForFlagWithDefault(
         kEmbeddedPageVersionFlagName,
         kEmbeddedPageVersionDefault,
         flags);
 
     // Check for themes.
     bool has_theme = false;
 #if !defined(OS_ANDROID)
     has_theme =
         !ThemeServiceFactory::GetForProfile(profile)->UsingDefaultTheme();
@@ skipping 59 matching lines @@
   if (!command_line->HasSwitch(switches::kInstantURL))
     return false;
 
   GURL instant_url(command_line->GetSwitchValueASCII(switches::kInstantURL));
   return url.scheme() == instant_url.scheme() &&
          url.host() == instant_url.host() &&
          url.port() == instant_url.port() &&
          url.path() == instant_url.path();
 }
 
-// Given a field trial group name in the above format, parses out the group
-// number and configuration flags.  Will return a group number of 0 on error.
-void GetFieldTrialInfo(const std::string& group_name,
+bool GetFieldTrialInfo(const std::string& group_name,
                        FieldTrialFlags* flags,
                        uint64* group_number) {
-  if (!EndsWith(group_name, kDisablingSuffix, true) &&
-      StartsWithASCII(group_name, kGroupNumberPrefix, true)) {
-    // We have a valid trial that starts with "Group" and isn't disabled.
-    size_t first_space = group_name.find(" ");
-    std::string group_prefix = group_name;
-    if (first_space != std::string::npos) {
-      // There is a flags section of the group name.  Split that out and parse
-      // it.
-      group_prefix = group_name.substr(0, first_space);
-      base::SplitStringIntoKeyValuePairs(
-          group_name.substr(first_space), ':', ' ', flags);
-    }
-    if (!base::StringToUint64(group_prefix.substr(strlen(kGroupNumberPrefix)),
-                              group_number)) {
-      // Could not parse group number.
-      *group_number = 0;
+  if (EndsWith(group_name, kDisablingSuffix, true) ||
+      !StartsWithASCII(group_name, kGroupNumberPrefix, true))
+    return false;

[MAD, 2013/01/31 20:14:53]

Nit: Multi-line conditions calls for {}

[robertshield, 2013/01/31 20:24:28]

Done.

+
+  // We have a valid trial that starts with "Group" and isn't disabled.
+  // First extract the flags.
+  std::string group_prefix(group_name);
+
+  size_t first_space = group_name.find(" ");
+  if (first_space != std::string::npos) {
+    // There is a flags section of the group name.  Split that out and parse
+    // it.
+    group_prefix = group_name.substr(0, first_space);
+    if (!base::SplitStringIntoKeyValuePairs(group_name.substr(first_space),
+                                            ':', ' ', flags)) {
+      // Failed to parse the flags section. Assume the whole group name is
+      // invalid.
+      return false;
     }
   }
+
+  // Now extract the group number, making sure we get a non-zero value.
+  uint64 temp_group_number = 0;
+  if (!base::StringToUint64(group_prefix.substr(strlen(kGroupNumberPrefix)),
+                            &temp_group_number) ||
+      temp_group_number == 0) {
+    return false;
+  }
+
+  if (group_number)
+    *group_number = temp_group_number;
+
+  return true;
 }
 
 // Given a FieldTrialFlags object, returns the string value of the provided
 // flag.
 std::string GetStringValueForFlagWithDefault(
     const std::string& flag,
     const std::string& default_value,
     FieldTrialFlags& flags) {
   FieldTrialFlags::const_iterator i;
   for (i = flags.begin(); i != flags.end(); i++) {
@@ skipping 16 matching lines @@
 
 // Given a FieldTrialFlags object, returns the boolean value of the provided
 // flag.
 bool GetBoolValueForFlagWithDefault(
     const std::string& flag, bool default_value, FieldTrialFlags& flags) {
   return !!GetUInt64ValueForFlagWithDefault(flag, default_value ? 1 : 0, flags);
 }
 
 }  // namespace search
 }  // namespace chrome