Merge to M100 beta: [Snooping protection] Decreased detection threshold.

Merge bug: b/224847948. This is a direct cherry-pick.

Our snooping model has been observed to make many more false negative
inferences than false positives. This CL reduces the threshold for
positive results to offset the effect.

(cherry picked from commit 017d428)

Bug: b:221167585
Change-Id: I32bad0eebdee6ecd3eecef1bfe02e33e329ea917
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3499530
Reviewed-by: Guoxing Zhao <charleszhao@chromium.org>
Commit-Queue: Michael Martis <martis@chromium.org>
Auto-Submit: Michael Martis <martis@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#977403}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3532444
Reviewed-by: Thanh Nguyen <thanhdng@chromium.org>
Commit-Queue: Thanh Nguyen <thanhdng@chromium.org>
Cr-Commit-Position: refs/branch-heads/4896@{#660}
Cr-Branched-From: 1f63ff4-refs/heads/main@{#972766}

ash/system/hps/hps_configuration.cc

@@ -54,11 +54,13 @@ absl::optional<int> GetIntParam(const base::FieldTrialParams& params,
 hps::FeatureConfig GetDefaultHpsNotifyFeatureConfig() {
   hps::FeatureConfig config;
 
-  auto& filter_config = *config.mutable_average_filter_config();
-  filter_config.set_average_window_size(3);
-  filter_config.set_positive_score_threshold(-30);
-  filter_config.set_negative_score_threshold(-30);
-  filter_config.set_default_uncertain_score(-128);
+  // Just apply a threshold to the last-seen inference.
+  auto& filter_config = *config.mutable_consecutive_results_filter_config();
+  filter_config.set_positive_count_threshold(1);
+  filter_config.set_negative_count_threshold(1);
+  filter_config.set_uncertain_count_threshold(1);
+  filter_config.set_positive_score_threshold(-50);
+  filter_config.set_negative_score_threshold(-50);
 
   return config;
 }

ash/system/hps/hps_configuration_unittest.cc

@@ -30,7 +30,7 @@ TEST(HpsFeatureConfigTest, EmptyParamsValid) {
   EXPECT_EQ(GetEnableHpsSenseConfig()->filter_config_case(),
             hps::FeatureConfig::kConsecutiveResultsFilterConfig);
   EXPECT_EQ(GetEnableHpsNotifyConfig()->filter_config_case(),
-            hps::FeatureConfig::kAverageFilterConfig);
+            hps::FeatureConfig::kConsecutiveResultsFilterConfig);
 }
 
 TEST(HpsFeatureConfigTest, ReturnNullIfTypeIsNotRecognizableHpsSense) {

chrome/browser/about_flags.cc

@@ -2692,25 +2692,28 @@ const FeatureEntry::Choice kDocumentTransitionSlowdownFactorChoices[] = {
 // sample.
 
 const FeatureEntry::FeatureParam kSnoopingProtectionPrecision[] = {
-    {"SnoopingProtection_filter_config_case", "3"},
-    {"SnoopingProtection_average_window_size", "3"},
-    {"SnoopingProtection_positive_score_threshold", "-30"},
-    {"SnoopingProtection_negative_score_threshold", "-30"},
-    {"SnoopingProtection_default_uncertain_score", "-128"}};
+    {"SnoopingProtection_filter_config_case", "2"},
+    {"SnoopingProtection_positive_count_threshold", "1"},
+    {"SnoopingProtection_negative_count_threshold", "1"},
+    {"SnoopingProtection_uncertain_count_threshold", "1"},
+    {"SnoopingProtection_positive_score_threshold", "-50"},
+    {"SnoopingProtection_negative_score_threshold", "-50"}};
 
 const FeatureEntry::FeatureParam kSnoopingProtectionConfidence[] = {
-    {"SnoopingProtection_filter_config_case", "3"},
-    {"SnoopingProtection_average_window_size", "5"},
-    {"SnoopingProtection_positive_score_threshold", "-30"},
-    {"SnoopingProtection_negative_score_threshold", "-30"},
-    {"SnoopingProtection_default_uncertain_score", "-128"}};
+    {"SnoopingProtection_filter_config_case", "2"},
+    {"SnoopingProtection_positive_count_threshold", "2"},
+    {"SnoopingProtection_negative_count_threshold", "2"},
+    {"SnoopingProtection_uncertain_count_threshold", "2"},
+    {"SnoopingProtection_positive_score_threshold", "-50"},
+    {"SnoopingProtection_negative_score_threshold", "-50"}};
 
 const FeatureEntry::FeatureParam kSnoopingProtectionRecall[] = {
-    {"SnoopingProtection_filter_config_case", "3"},
-    {"SnoopingProtection_average_window_size", "3"},
+    {"SnoopingProtection_filter_config_case", "2"},
+    {"SnoopingProtection_positive_count_threshold", "1"},
+    {"SnoopingProtection_negative_count_threshold", "1"},
+    {"SnoopingProtection_uncertain_count_threshold", "1"},
     {"SnoopingProtection_positive_score_threshold", "-70"},
-    {"SnoopingProtection_negative_score_threshold", "-70"},
-    {"SnoopingProtection_default_uncertain_score", "-128"}};
+    {"SnoopingProtection_negative_score_threshold", "-70"}};
 
 const FeatureEntry::FeatureVariation kSnoopingProtectionVariations[] = {
     {"Precise", kSnoopingProtectionPrecision,