Plumbing for variations headers from synthetic field trials.

BUG=428055

Review URL: https://codereview.chromium.org/688973004

Cr-Commit-Position: refs/heads/master@{#302331}

10 files changed, 112 insertions, 24 deletions

diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index 6ab5340..48e78ea 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -623,6 +623,7 @@ void ChromeBrowserMainParts::SetupMetricsAndFieldTrials() {
         command_line->GetSwitchValueASCII(switches::kForceVariationIds));
     CHECK(result) << "Invalid --" << switches::kForceVariationIds
                   << " list specified.";
+    metrics->AddSyntheticTrialObserver(provider);
   }
   chrome_variations::VariationsService* variations_service =
       browser_process_->variations_service();
diff --git a/components/metrics/metrics_service.cc b/components/metrics/metrics_service.cc
index 4db3bb5..4fa2e75 100644
--- a/components/metrics/metrics_service.cc
+++ b/components/metrics/metrics_service.cc
@@ -1138,6 +1138,18 @@ bool MetricsService::UmaMetricsProperlyShutdown() {
   return clean_shutdown_status_ == CLEANLY_SHUTDOWN;
 }
 
+void MetricsService::AddSyntheticTrialObserver(
+    SyntheticTrialObserver* observer) {
+  synthetic_trial_observer_list_.AddObserver(observer);
+  if (!synthetic_trial_groups_.empty())
+    observer->OnSyntheticTrialsChanged(synthetic_trial_groups_);
+}
+
+void MetricsService::RemoveSyntheticTrialObserver(
+    SyntheticTrialObserver* observer) {
+  synthetic_trial_observer_list_.RemoveObserver(observer);
+}
+
 void MetricsService::RegisterSyntheticFieldTrial(
     const SyntheticTrialGroup& trial) {
   for (size_t i = 0; i < synthetic_trial_groups_.size(); ++i) {
@@ -1145,6 +1157,7 @@ void MetricsService::RegisterSyntheticFieldTrial(
       if (synthetic_trial_groups_[i].id.group != trial.id.group) {
         synthetic_trial_groups_[i].id.group = trial.id.group;
         synthetic_trial_groups_[i].start_time = base::TimeTicks::Now();
+        NotifySyntheticTrialObservers();
       }
       return;
     }
@@ -1153,6 +1166,7 @@ void MetricsService::RegisterSyntheticFieldTrial(
   SyntheticTrialGroup trial_group = trial;
   trial_group.start_time = base::TimeTicks::Now();
   synthetic_trial_groups_.push_back(trial_group);
+  NotifySyntheticTrialObservers();
 }
 
 void MetricsService::RegisterMetricsProvider(
@@ -1166,6 +1180,11 @@ void MetricsService::CheckForClonedInstall(
   state_manager_->CheckForClonedInstall(task_runner);
 }
 
+void MetricsService::NotifySyntheticTrialObservers() {
+  FOR_EACH_OBSERVER(SyntheticTrialObserver, synthetic_trial_observer_list_,
+                    OnSyntheticTrialsChanged(synthetic_trial_groups_));
+}
+
 void MetricsService::GetCurrentSyntheticFieldTrials(
     std::vector<variations::ActiveGroupId>* synthetic_trials) {
   DCHECK(synthetic_trials);
diff --git a/components/metrics/metrics_service.h b/components/metrics/metrics_service.h
index eae44f3..19794ea 100644
--- a/components/metrics/metrics_service.h
+++ b/components/metrics/metrics_service.h
@@ -21,6 +21,7 @@
 #include "base/metrics/histogram_flattener.h"
 #include "base/metrics/histogram_snapshot_manager.h"
 #include "base/metrics/user_metrics.h"
+#include "base/observer_list.h"
 #include "base/time/time.h"
 #include "components/metrics/clean_exit_beacon.h"
 #include "components/metrics/metrics_log.h"
@@ -76,6 +77,17 @@ struct SyntheticTrialGroup {
   SyntheticTrialGroup(uint32 trial, uint32 group);
 };
 
+// Interface class to observe changes to synthetic trials in MetricsService.
+class SyntheticTrialObserver {
+ public:
+  // Called when the list of synthetic field trial groups has changed.
+  virtual void OnSyntheticTrialsChanged(
+      const std::vector<SyntheticTrialGroup>& groups) = 0;
+
+ protected:
+  virtual ~SyntheticTrialObserver() {}
+};
+
 // See metrics_service.cc for a detailed description.
 class MetricsService : public base::HistogramFlattener {
  public:
@@ -211,6 +223,12 @@ class MetricsService : public base::HistogramFlattener {
   // To use this method, SyntheticTrialGroup should friend your class.
   void RegisterSyntheticFieldTrial(const SyntheticTrialGroup& trial_group);
 
+  // Adds an observer to be notified when the synthetic trials list changes.
+  void AddSyntheticTrialObserver(SyntheticTrialObserver* observer);
+
+  // Removes an existing observer of synthetic trials list changes.
+  void RemoveSyntheticTrialObserver(SyntheticTrialObserver* observer);
+
   // Register the specified |provider| to provide additional metrics into the
   // UMA log. Should be called during MetricsService initialization only.
   void RegisterMetricsProvider(scoped_ptr<MetricsProvider> provider);
@@ -358,6 +376,9 @@ class MetricsService : public base::HistogramFlattener {
   // Sets the value of the specified path in prefs and schedules a save.
   void RecordBooleanPrefValue(const char* path, bool value);
 
+  // Notifies observers on a synthetic trial list change.
+  void NotifySyntheticTrialObservers();
+
   // Returns a list of synthetic field trials that were active for the entire
   // duration of the current log.
   void GetCurrentSyntheticFieldTrials(
@@ -447,6 +468,9 @@ class MetricsService : public base::HistogramFlattener {
   // Field trial groups that map to Chrome configuration states.
   SyntheticTrialGroups synthetic_trial_groups_;
 
+  // List of observers of |synthetic_trial_groups_| changes.
+  ObserverList<SyntheticTrialObserver> synthetic_trial_observer_list_;
+
   // Execution phase the browser is in.
   static ExecutionPhase execution_phase_;
 
diff --git a/components/variations.gypi b/components/variations.gypi
index ee3a412..bf2cc37 100644
--- a/components/variations.gypi
+++ b/components/variations.gypi
@@ -71,6 +71,7 @@
       'dependencies': [
         '../base/base.gyp:base',
         'components.gyp:google_core_browser',
+        "components.gyp:metrics",
         'variations',
       ],
       'sources': [
diff --git a/components/variations/net/BUILD.gn b/components/variations/net/BUILD.gn
index e35f5a84..34158fe 100644
--- a/components/variations/net/BUILD.gn
+++ b/components/variations/net/BUILD.gn
@@ -12,6 +12,7 @@ source_set("net") {
   deps = [
     "//base",
     "//components/google/core/browser",
+    "//components/metrics",
     "//components/variations/proto",
     "//net",
   ]
diff --git a/components/variations/net/DEPS b/components/variations/net/DEPS
index f4a5acd..1abc71b 100644
--- a/components/variations/net/DEPS
+++ b/components/variations/net/DEPS
@@ -1,4 +1,5 @@
 include_rules = [
   "+components/google",
+  "+components/metrics",
   "+net",
 ]
diff --git a/components/variations/net/variations_http_header_provider.cc b/components/variations/net/variations_http_header_provider.cc
index 1220fae..fa630cf 100644
--- a/components/variations/net/variations_http_header_provider.cc
+++ b/components/variations/net/variations_http_header_provider.cc
@@ -137,6 +137,20 @@ void VariationsHttpHeaderProvider::OnFieldTrialGroupFinalized(
   UpdateVariationIDsHeaderValue();
 }
 
+void VariationsHttpHeaderProvider::OnSyntheticTrialsChanged(
+    const std::vector<metrics::SyntheticTrialGroup>& groups) {
+  base::AutoLock scoped_lock(lock_);
+
+  synthetic_variation_ids_set_.clear();
+  for (const metrics::SyntheticTrialGroup& group : groups) {
+    const VariationID id =
+        GetGoogleVariationIDFromHashes(GOOGLE_WEB_PROPERTIES, group.id);
+    if (id != EMPTY_ID)
+      synthetic_variation_ids_set_.insert(id);
+  }
+  UpdateVariationIDsHeaderValue();
+}
+
 void VariationsHttpHeaderProvider::InitVariationIDsCacheIfNeeded() {
   base::AutoLock scoped_lock(lock_);
   if (variation_ids_cache_initialized_)
@@ -186,7 +200,8 @@ void VariationsHttpHeaderProvider::UpdateVariationIDsHeaderValue() {
   variation_ids_header_.clear();
 
   if (variation_ids_set_.empty() && default_variation_ids_set_.empty() &&
-      variation_trigger_ids_set_.empty() && default_trigger_id_set_.empty()) {
+      variation_trigger_ids_set_.empty() && default_trigger_id_set_.empty() &&
+      synthetic_variation_ids_set_.empty()) {
     return;
   }
 
@@ -203,26 +218,20 @@ void VariationsHttpHeaderProvider::UpdateVariationIDsHeaderValue() {
 
   // Merge the two sets of experiment ids.
   std::set<VariationID> all_variation_ids_set = default_variation_ids_set_;
-  for (std::set<VariationID>::const_iterator it = variation_ids_set_.begin();
-       it != variation_ids_set_.end(); ++it) {
-    all_variation_ids_set.insert(*it);
-  }
-  ClientVariations proto;
-  for (std::set<VariationID>::const_iterator it = all_variation_ids_set.begin();
-       it != all_variation_ids_set.end(); ++it) {
-    proto.add_variation_id(*it);
-  }
+  for (VariationID id : variation_ids_set_)
+    all_variation_ids_set.insert(id);
+  for (VariationID id : synthetic_variation_ids_set_)
+    all_variation_ids_set.insert(id);
 
   std::set<VariationID> all_trigger_ids_set = default_trigger_id_set_;
-  for (std::set<VariationID>::const_iterator it =
-           variation_trigger_ids_set_.begin();
-       it != variation_trigger_ids_set_.end(); ++it) {
-    all_trigger_ids_set.insert(*it);
-  }
-  for (std::set<VariationID>::const_iterator it = all_trigger_ids_set.begin();
-       it != all_trigger_ids_set.end(); ++it) {
-    proto.add_trigger_variation_id(*it);
-  }
+  for (VariationID id : variation_trigger_ids_set_)
+    all_trigger_ids_set.insert(id);
+
+  ClientVariations proto;
+  for (VariationID id : all_variation_ids_set)
+    proto.add_variation_id(id);
+  for (VariationID id : all_trigger_ids_set)
+    proto.add_trigger_variation_id(id);
 
   std::string serialized;
   proto.SerializeToString(&serialized);
diff --git a/components/variations/net/variations_http_header_provider.h b/components/variations/net/variations_http_header_provider.h
index a0e3046..0a511cc 100644
--- a/components/variations/net/variations_http_header_provider.h
+++ b/components/variations/net/variations_http_header_provider.h
@@ -7,11 +7,13 @@
 
 #include <set>
 #include <string>
+#include <vector>
 
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
 #include "base/metrics/field_trial.h"
 #include "base/synchronization/lock.h"
+#include "components/metrics/metrics_service.h"
 #include "components/variations/variations_associated_data.h"
 
 namespace content {
@@ -31,7 +33,8 @@ namespace variations {
 // A helper class for maintaining client experiments and metrics state
 // transmitted in custom HTTP request headers.
 // This class is a thread-safe singleton.
-class VariationsHttpHeaderProvider : base::FieldTrialList::Observer {
+class VariationsHttpHeaderProvider : public base::FieldTrialList::Observer,
+                                     public metrics::SyntheticTrialObserver {
  public:
   static VariationsHttpHeaderProvider* GetInstance();
 
@@ -66,12 +69,16 @@ class VariationsHttpHeaderProvider : base::FieldTrialList::Observer {
   VariationsHttpHeaderProvider();
   ~VariationsHttpHeaderProvider() override;
 
-  // base::FieldTrialList::Observer implementation.
+  // base::FieldTrialList::Observer:
   // This will add the variation ID associated with |trial_name| and
   // |group_name| to the variation ID cache.
   void OnFieldTrialGroupFinalized(const std::string& trial_name,
                                   const std::string& group_name) override;
 
+  // metrics::SyntheticTrialObserver:
+  void OnSyntheticTrialsChanged(
+      const std::vector<metrics::SyntheticTrialGroup>& groups) override;
+
   // Prepares the variation IDs cache with initial values if not already done.
   // This method also registers the caller with the FieldTrialList to receive
   // new variation IDs.
@@ -102,6 +109,9 @@ class VariationsHttpHeaderProvider : base::FieldTrialList::Observer {
   std::set<VariationID> default_variation_ids_set_;
   std::set<VariationID> default_trigger_id_set_;
 
+  // Variations ids from synthetic field trials.
+  std::set<VariationID> synthetic_variation_ids_set_;
+
   std::string variation_ids_header_;
 
   DISALLOW_COPY_AND_ASSIGN(VariationsHttpHeaderProvider);
diff --git a/components/variations/variations_associated_data.cc b/components/variations/variations_associated_data.cc
index 6ef2343..857ded5 100644
--- a/components/variations/variations_associated_data.cc
+++ b/components/variations/variations_associated_data.cc
@@ -184,17 +184,29 @@ void AssociateGoogleVariationIDForce(IDCollectionKey key,
                                      const std::string& trial_name,
                                      const std::string& group_name,
                                      VariationID id) {
-  GroupMapAccessor::GetInstance()->AssociateID(
-      key, MakeActiveGroupId(trial_name, group_name), id, true);
+  AssociateGoogleVariationIDForceHashes(
+      key, MakeActiveGroupId(trial_name, group_name), id);
+}
+
+void AssociateGoogleVariationIDForceHashes(IDCollectionKey key,
+                                           const ActiveGroupId& active_group,
+                                           VariationID id) {
+  GroupMapAccessor::GetInstance()->AssociateID(key, active_group, id, true);
 }
 
 VariationID GetGoogleVariationID(IDCollectionKey key,
                                  const std::string& trial_name,
                                  const std::string& group_name) {
-  return GroupMapAccessor::GetInstance()->GetID(
+  return GetGoogleVariationIDFromHashes(
       key, MakeActiveGroupId(trial_name, group_name));
 }
 
+VariationID GetGoogleVariationIDFromHashes(
+    IDCollectionKey key,
+    const ActiveGroupId& active_group) {
+  return GroupMapAccessor::GetInstance()->GetID(key, active_group);
+}
+
 bool AssociateVariationParams(
     const std::string& trial_name,
     const std::string& group_name,
diff --git a/components/variations/variations_associated_data.h b/components/variations/variations_associated_data.h
index 8bacae1..3fe70f8 100644
--- a/components/variations/variations_associated_data.h
+++ b/components/variations/variations_associated_data.h
@@ -82,6 +82,11 @@ void AssociateGoogleVariationIDForce(IDCollectionKey key,
                                      const std::string& group_name,
                                      VariationID id);
 
+// As above, but takes an ActiveGroupId hash pair, rather than the string names.
+void AssociateGoogleVariationIDForceHashes(IDCollectionKey key,
+                                           const ActiveGroupId& active_group,
+                                           VariationID id);
+
 // Retrieve the variations::VariationID associated with a FieldTrial group for
 // collection |key|. The group is denoted by |trial_name| and |group_name|.
 // This will return variations::kEmptyID if there is currently no associated ID
@@ -92,6 +97,11 @@ VariationID GetGoogleVariationID(IDCollectionKey key,
                                  const std::string& trial_name,
                                  const std::string& group_name);
 
+// Same as GetGoogleVariationID(), but takes in a hashed |active_group| rather
+// than the string trial and group name.
+VariationID GetGoogleVariationIDFromHashes(IDCollectionKey key,
+                                           const ActiveGroupId& active_group);
+
 // Associates the specified set of key-value |params| with the variation
 // specified by |trial_name| and |group_name|. Fails and returns false if the
 // specified variation already has params associated with it or the field trial