Revert "Increase FRE Source Trial percentages on Stable."

This reverts commit 17efb4a8181d21cbef5b2a3c7d82507b216633ea.

Reason for revert: There is a bug in the assignment of the groups

Original change's description:
> Increase FRE Source Trial percentages on Stable.
>
> The enabled and control groups for the FRE Source Trial on the Stable channel are increased from 1% to 20%, with the default group adjusted accordingly.
>
> The trial is only being run in iOS.
>
> https://uma.googleplex.com/p/chrome/variations?sid=6cb0b62348f1b04d33a1f4c66f711751
>
> DO NOT MERGE
>
> Bug: 407991309
> Change-Id: I63fee3ee74cdd9b5a51163f6c88ec80a1b0a332f
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6905454
> Reviewed-by: Caitlin Fischer <caitlinfischer@google.com>
> Commit-Queue: Ramon Cano Aparicio <rcanoaparicio@google.com>
> Cr-Commit-Position: refs/heads/main@{#1513029}

Bug: 407991309
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I088eed85981109042ceb3277f051160c27465ddf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6929947
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Ramon Cano Aparicio <rcanoaparicio@google.com>
Reviewed-by: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/main@{#1513077}
NOKEYCHECK=True
GitOrigin-RevId: 74d2920869420985fcef8bf251813ca153a10926

file_metrics_provider_unittest.cc

diff --git a/file_metrics_provider_unittest.cc b/file_metrics_provider_unittest.cc
index 6b07ce4..337bbb6 100644
--- a/file_metrics_provider_unittest.cc
+++ b/file_metrics_provider_unittest.cc
@@ -1493,9 +1493,7 @@
                          FileMetricsProviderFRETrialFirstRunGroupsTest,
                          testing::Values(fre_source_trial::kDefaultGroup,
                                          fre_source_trial::kControlGroup,
-                                         fre_source_trial::kEnabledGroup,
-                                         fre_source_trial::kControlGroup20,
-                                         fre_source_trial::kEnabledGroup20));
+                                         fre_source_trial::kEnabledGroup));
 
 TEST_P(FileMetricsProviderFRETrialFirstRunGroupsTest, FRETrialKeepTrialGroup) {
   const std::string_view trial_group = GetParam();
@@ -1544,8 +1542,7 @@
 
   task_environment()->RunUntilIdle();
 
-  bool should_keep_dir = trial_group == fre_source_trial::kEnabledGroup ||
-                         trial_group == fre_source_trial::kEnabledGroup20;
+  bool should_keep_dir = trial_group == fre_source_trial::kEnabledGroup;
   EXPECT_EQ(base::PathExists(dir), should_keep_dir);
 }
 
@@ -1557,9 +1554,7 @@
                          FileMetricsProviderFRETrialSubsequentRunGroupsTest,
                          testing::Values(fre_source_trial::kDefaultGroup,
                                          fre_source_trial::kControlGroup,
-                                         fre_source_trial::kEnabledGroup,
-                                         fre_source_trial::kControlGroup20,
-                                         fre_source_trial::kEnabledGroup20));
+                                         fre_source_trial::kEnabledGroup));
 
 TEST_P(FileMetricsProviderFRETrialSubsequentRunGroupsTest, FRETrialPostFRERun) {
   const std::string_view trial_group = GetParam();

fre_source_trial.cc

diff --git a/fre_source_trial.cc b/fre_source_trial.cc
index 6dd401f..5b4f18f 100644
--- a/fre_source_trial.cc
+++ b/fre_source_trial.cc
@@ -27,8 +27,6 @@
     version_info::Channel channel) {
   int enabled_percent = 0;
   int control_percent = 0;
-  int enabled_20_percent = 0;
-  int control_20_percent = 0;
   int default_percent = 100;
   switch (channel) {
     case version_info::Channel::CANARY:
@@ -41,9 +39,7 @@
     case version_info::Channel::STABLE:
       enabled_percent = 1;
       control_percent = 1;
-      enabled_20_percent = 20;
-      control_20_percent = 20;
-      default_percent = 58;
+      default_percent = 98;
       break;
     default:
       break;
@@ -53,8 +49,6 @@
   scoped_refptr<base::FieldTrial> trial = CreateFieldTrial(entropy_provider);
   trial->AppendGroup(kEnabledGroup, enabled_percent);
   trial->AppendGroup(kControlGroup, control_percent);
-  trial->AppendGroup(kEnabledGroup20, enabled_20_percent);
-  trial->AppendGroup(kControlGroup, control_20_percent);
   trial->AppendGroup(kDefaultGroup, default_percent);
 
   // Finalize the group choice. `group_name()` calls `Activate()` internally.
@@ -76,9 +70,7 @@
 }
 
 bool IsEnabled() {
-  const std::string& group_name =
-      base::FieldTrialList::FindFullName(kFRESourceTrial);
-  return group_name == kEnabledGroup || group_name == kEnabledGroup20;
+  return base::FieldTrialList::FindFullName(kFRESourceTrial) == kEnabledGroup;
 }
 
 void Create(PrefService* local_state,

fre_source_trial.h

diff --git a/fre_source_trial.h b/fre_source_trial.h
index 558e9a6..396452b 100644
--- a/fre_source_trial.h
+++ b/fre_source_trial.h
@@ -18,9 +18,6 @@
 inline constexpr char kDefaultGroup[] = "Default";
 inline constexpr char kControlGroup[] = "Control";
 inline constexpr char kEnabledGroup[] = "Enabled";
-// Groups for the 20% stable experiment.
-inline constexpr char kControlGroup20[] = "Control_20";
-inline constexpr char kEnabledGroup20[] = "Enabled_20";
 
 // Registers the local state prefs for the FileMetricsProvider FRE trial.
 void RegisterLocalStatePrefs(PrefRegistrySimple* registry);