Create Field Trial param for whitelisting UKM Entries.

components/ukm/ukm_service.h

 // Copyright 2017 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.
 
 #ifndef COMPONENTS_UKM_UKM_SERVICE_H_
 #define COMPONENTS_UKM_UKM_SERVICE_H_
 
 #include <stddef.h>
 #include <memory>
 #include <vector>
@@ skipping 93 matching lines @@
   }
 
  private:
   friend UkmPageLoadMetricsObserver;
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, AddEntryOnlyWithNonEmptyMetrics);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, EntryBuilderAndSerialization);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest,
                            LogsUploadedOnlyWhenHavingSourcesOrEntries);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, MetricsProviderTest);
   FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, PersistAndPurge);
+  FRIEND_TEST_ALL_PREFIXES(UkmServiceTest, WhitelistEntryTest);
 
   // Get a new UkmEntryBuilder object for the specified source ID and event,
   // which can get metrics added to.
   //
   // This API being private is intentional. Any client using UKM needs to
   // declare itself to be a friend of UkmService and go through code review
   // process.
   std::unique_ptr<UkmEntryBuilder> GetEntryBuilder(int32_t source_id,
                                                    const char* event_name);
 
@@ skipping 18 matching lines @@
 
   // Starts an upload of the next log from persisted_logs_.
   void StartScheduledUpload();
 
   // Called by log_uploader_ when the an upload is completed.
   void OnLogUploadComplete(int response_code);
 
   // Add an entry to the UkmEntry list.
   void AddEntry(std::unique_ptr<UkmEntry> entry);
 
+  // Cache the list of whitelisted entries from the field trial parameter.
+  void StoreWhitelistedEntries();
+
   // A weak pointer to the PrefService used to read and write preferences.
   PrefService* pref_service_;
 
   // Whether recording new data is currently allowed.
   bool recording_enabled_;
 
   // The UKM client id stored in prefs.
   uint64_t client_id_;
 
   // The UKM session id stored in prefs.
@@ skipping 20 matching lines @@
   bool initialize_started_;
   bool initialize_complete_;
   bool log_upload_in_progress_;
 
   // Contains newly added sources and entries of UKM metrics which periodically
   // get serialized and cleared by BuildAndStoreLog().
   // TODO(zhenw): update sources to a map keyed by source ID.
   std::vector<std::unique_ptr<UkmSource>> sources_;
   std::vector<std::unique_ptr<UkmEntry>> entries_;
 
+  // Whitelisted Entry hashes, only the ones in this set will be recorded.
+  std::set<uint64_t> whitelisted_entry_hashes_;
+
   // Weak pointers factory used to post task on different threads. All weak
   // pointers managed by this factory have the same lifetime as UkmService.
   base::WeakPtrFactory<UkmService> self_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UkmService);
 };
 
 }  // namespace ukm
 
 #endif  // COMPONENTS_UKM_UKM_SERVICE_H_