Add field trial name/group to hints request

Bug: 1112970
Change-Id: I6d8fbbb236a185bec828d11720407b66aee3f8c5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2337287
Commit-Queue: Sophie Chang <sophiechang@chromium.org>
Reviewed-by: Michael Crouse <mcrouse@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795755}

chrome/browser/optimization_guide/hints_fetcher_browsertest.cc

@@ -41,6 +41,7 @@
 #include "components/optimization_guide/top_host_provider.h"
 #include "components/prefs/pref_service.h"
 #include "components/ukm/test_ukm_recorder.h"
+#include "components/variations/hashing.h"
 #include "content/public/browser/browser_task_traits.h"
 #include "content/public/test/browser_test.h"
 #include "content/public/test/browser_test_base.h"
@@ -457,6 +458,12 @@ class HintsFetcherDisabledBrowserTest : public InProcessBrowserTest {
       hosts_and_urls_requested.erase(host_or_url);
     }
     EXPECT_EQ(0u, hosts_and_urls_requested.size());
+
+    // We only expect 1 field trial to be allowed and sent up.
+    EXPECT_EQ(1, hints_request.active_field_trials_size());
+    EXPECT_EQ(variations::HashName(
+                  "scoped_feature_list_trial_for_OptimizationHintsFetching"),
+              hints_request.active_field_trials(0).name_hash());
   }
 
   void TearDownOnMainThread() override {
@@ -509,6 +516,9 @@ class HintsFetcherBrowserTest : public HintsFetcherDisabledBrowserTest {
             {optimization_guide::features::kOptimizationHints, {}},
             {optimization_guide::features::kRemoteOptimizationGuideFetching,
              {{"max_concurrent_page_navigation_fetches", "2"}}},
+            {optimization_guide::features::kOptimizationHintsFieldTrials,
+             {{"allowed_field_trial_names",
+               "scoped_feature_list_trial_for_OptimizationHintsFetching"}}},
         },
         {});
     // Call to inherited class to match same set up with feature flags added.

components/optimization_guide/hints_fetcher.cc

@@ -17,6 +17,7 @@
 #include "components/optimization_guide/proto/hints.pb.h"
 #include "components/prefs/pref_service.h"
 #include "components/prefs/scoped_user_pref_update.h"
+#include "components/variations/active_field_trials.h"
 #include "components/variations/net/variations_http_headers.h"
 #include "content/public/browser/network_service_instance.h"
 #include "net/base/load_flags.h"
@@ -90,6 +91,8 @@ HintsFetcher::HintsFetcher(
   url_loader_factory_ = std::move(url_loader_factory);
   CHECK(optimization_guide_service_url_.SchemeIs(url::kHttpsScheme));
   DCHECK(features::IsRemoteFetchingEnabled());
+  allowed_field_trial_name_hashes_ =
+      features::FieldTrialNameHashesAllowedForFetch();
 }
 
 HintsFetcher::~HintsFetcher() {
@@ -202,6 +205,30 @@ bool HintsFetcher::FetchOptimizationGuideServiceHints(
 
   get_hints_request.set_context(request_context_);
 
+  if (!allowed_field_trial_name_hashes_.empty()) {
+    std::vector<variations::ActiveGroupId> active_field_trials;
+    variations::GetFieldTrialActiveGroupIds(/*suffix=*/"",
+                                            &active_field_trials);
+    for (const auto& active_field_trial : active_field_trials) {
+      if (static_cast<size_t>(get_hints_request.active_field_trials_size()) ==
+          allowed_field_trial_name_hashes_.size()) {
+        // We've found all the field trials that we are allowed to send to the
+        // server.
+        break;
+      }
+
+      if (allowed_field_trial_name_hashes_.find(active_field_trial.name) ==
+          allowed_field_trial_name_hashes_.end()) {
+        // Continue if we are not allowed to send the field trial to the server.
+        continue;
+      }
+
+      proto::FieldTrial* ft_proto = get_hints_request.add_active_field_trials();
+      ft_proto->set_name_hash(active_field_trial.name);
+      ft_proto->set_group_hash(active_field_trial.group);
+    }
+  }
+
   for (const auto& url : valid_urls)
     get_hints_request.add_urls()->set_url(url.spec());
 

components/optimization_guide/hints_fetcher.h

@@ -163,6 +163,10 @@ class HintsFetcher {
   // retrieving hints from the remote Optimization Guide Service.
   base::TimeTicks hints_fetch_start_time_;
 
+  // Field trial name hashes that are allowed to be sent up in the request to
+  // the remote Optimization Guide Service.
+  base::flat_set<uint32_t> allowed_field_trial_name_hashes_;
+
   SEQUENCE_CHECKER(sequence_checker_);
 
   DISALLOW_COPY_AND_ASSIGN(HintsFetcher);

components/optimization_guide/optimization_guide_features.cc

@@ -13,6 +13,7 @@
 #include "build/build_config.h"
 #include "components/optimization_guide/optimization_guide_constants.h"
 #include "components/optimization_guide/optimization_guide_switches.h"
+#include "components/variations/hashing.h"
 #include "google_apis/google_api_keys.h"
 #include "net/base/url_util.h"
 
@@ -42,6 +43,11 @@ const base::Feature kOptimizationHints {
 const base::Feature kOptimizationHintsExperiments{
     "OptimizationHintsExperiments", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Feature flag that contains a feature param that specifies the field trials
+// that are allowed to be sent up to the Optimization Guide Server.
+const base::Feature kOptimizationHintsFieldTrials{
+    "OptimizationHintsFieldTrials", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enables fetching from a remote Optimization Guide Service.
 const base::Feature kRemoteOptimizationGuideFetching {
   "OptimizationHintsFetching",
@@ -292,6 +298,22 @@ base::flat_set<std::string> ExternalAppPackageNamesApprovedForFetch() {
                                      app_packages_list.end());
 }
 
+base::flat_set<uint32_t> FieldTrialNameHashesAllowedForFetch() {
+  std::string value = base::GetFieldTrialParamValueByFeature(
+      kOptimizationHintsFieldTrials, "allowed_field_trial_names");
+  if (value.empty())
+    return {};
+
+  std::vector<std::string> allowed_field_trial_names = base::SplitString(
+      value, ",", base::TRIM_WHITESPACE, base::SPLIT_WANT_NONEMPTY);
+  base::flat_set<uint32_t> allowed_field_trial_name_hashes;
+  for (const auto& allowed_field_trial_name : allowed_field_trial_names) {
+    allowed_field_trial_name_hashes.insert(
+        variations::HashName(allowed_field_trial_name));
+  }
+  return allowed_field_trial_name_hashes;
+}
+
 bool ShouldUseMLServiceForPrediction() {
   return base::FeatureList::IsEnabled(
       kOptimizationTargetPredictionUsingMLService);

components/optimization_guide/optimization_guide_features.h

@@ -21,6 +21,7 @@ namespace features {
 
 extern const base::Feature kOptimizationHints;
 extern const base::Feature kOptimizationHintsExperiments;
+extern const base::Feature kOptimizationHintsFieldTrials;
 constexpr char kOptimizationHintsExperimentNameParam[] = "experiment_name";
 extern const base::Feature kRemoteOptimizationGuideFetching;
 extern const base::Feature kRemoteOptimizationGuideFetchingAnonymousDataConsent;
@@ -151,6 +152,11 @@ int PredictionModelFetchRandomMaxDelaySecs();
 // approved for fetching from the remote Optimization Guide Service.
 base::flat_set<std::string> ExternalAppPackageNamesApprovedForFetch();
 
+// Returns a set of field trial name hashes that can be sent in the request to
+// the remote Optimization Guide Service if the client is in one of the
+// specified field trials.
+base::flat_set<uint32_t> FieldTrialNameHashesAllowedForFetch();
+
 // Whether out-of-process model evaluation via the ML Service is enabled.
 bool ShouldUseMLServiceForPrediction();
 

components/optimization_guide/proto/hints.proto

@@ -39,6 +39,13 @@ message UrlInfo {
   optional string url = 1;
 }
 
+message FieldTrial {
+  // The hash of a field trial.
+  optional uint32 name_hash = 1;
+  // The hash of the active group within the field trial.
+  optional uint32 group_hash = 2;
+}
+
 // Request to return a set of hints that guide what optimizations to perform
 // on those hosts.
 message GetHintsRequest {
@@ -64,6 +71,9 @@ message GetHintsRequest {
 
   // Context in which this request is made.
   optional RequestContext context = 3;
+
+  // The field trials that are currently active when this request is made.
+  repeated FieldTrial active_field_trials = 6;
 }
 
 // Response to the GetHints request.