P3A: Remove alternate log store.

Now that we only have one message format, replace the parallel
log stores with a single one.

Follow-up to brave/brave-browser#15967

components/p3a/brave_p3a_log_store.cc

@@ -119,15 +119,7 @@ const std::string& BraveP3ALogStore::staged_log() const {
   auto iter = log_.find(staged_entry_key_);
   DCHECK(iter != log_.end());
 
-  return staged_log_.legacy_log;
-}
-
-const std::string& BraveP3ALogStore::staged_json_log() const {
-  DCHECK(!staged_entry_key_.empty());
-  auto iter = log_.find(staged_entry_key_);
-  DCHECK(iter != log_.end());
-
-  return staged_log_.json_log;
+  return staged_log_;
 }
 
 std::string BraveP3ALogStore::staged_log_type() const {

components/p3a/brave_p3a_log_store.h

@@ -26,21 +26,11 @@ namespace brave {
 // for now persisted entries never expire.
 class BraveP3ALogStore : public metrics::LogStore {
  public:
-  struct LogForJsonMigration {
-    std::string legacy_log;
-    std::string json_log;
-
-    void clear() {
-      legacy_log.clear();
-      json_log.clear();
-    }
-  };
-
   class Delegate {
    public:
     // Prepares a string representaion of an entry.
-    virtual LogForJsonMigration Serialize(base::StringPiece histogram_name,
-                                          uint64_t value) = 0;
+    virtual std::string Serialize(base::StringPiece histogram_name,
+                                  uint64_t value) = 0;
     // Returns false if the metric is obsolete and should be cleaned up.
     virtual bool IsActualMetric(base::StringPiece histogram_name) const = 0;
     virtual ~Delegate() {}
@@ -63,8 +53,6 @@ class BraveP3ALogStore : public metrics::LogStore {
   bool has_unsent_logs() const override;
   bool has_staged_log() const override;
   const std::string& staged_log() const override;
-  // This will replace `staged_log` once we migrate to JSON pings.
-  const std::string& staged_json_log() const;
   std::string staged_log_type() const;
   const std::string& staged_log_hash() const override;
   const std::string& staged_log_signature() const override;
@@ -105,7 +93,7 @@ class BraveP3ALogStore : public metrics::LogStore {
   base::flat_set<std::string> unsent_entries_;
 
   std::string staged_entry_key_;
-  LogForJsonMigration staged_log_;
+  std::string staged_log_;
 
   // Not used for now.
   std::string staged_log_hash_;

components/p3a/brave_p3a_service.cc

@@ -14,7 +14,6 @@
 #include "base/json/json_writer.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/histogram_samples.h"
-#include "base/metrics/metrics_hashes.h"
 #include "base/metrics/sample_vector.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/no_destructor.h"
@@ -180,27 +179,21 @@ void BraveP3AService::Init(
   }
 }
 
-BraveP3ALogStore::LogForJsonMigration BraveP3AService::Serialize(
-    base::StringPiece histogram_name,
-    uint64_t value) {
+std::string BraveP3AService::Serialize(base::StringPiece histogram_name,
+                                       uint64_t value) {
   // TRACE_EVENT0("brave_p3a", "SerializeMessage");
   // TODO(iefremov): Maybe we should store it in logs and pass here?
   // We cannot directly query |base::StatisticsRecorder::FindHistogram| because
   // the serialized value can be obtained from persisted log storage at the
   // point when the actual histogram is not ready yet.
-  const uint64_t histogram_name_hash = base::HashMetricName(histogram_name);
-
   UpdateMessageMeta();
-  brave_pyxis::RawP3AValue message;
-  GenerateP3AMessage(histogram_name_hash, value, message_meta_, &message);
-
   base::Value p3a_json_value =
       GenerateP3AMessageDict(histogram_name, value, message_meta_);
   std::string p3a_json_message;
   const bool ok = base::JSONWriter::Write(p3a_json_value, &p3a_json_message);
   DCHECK(ok);
 
-  return {message.SerializeAsString(), p3a_json_message};
+  return p3a_json_message;
 }
 
 bool
@@ -297,7 +290,7 @@ void BraveP3AService::StartScheduledUpload() {
     const std::string log_type = log_store_->staged_log_type();
     VLOG(2) << "StartScheduledUpload - Uploading " << log.size() << " bytes "
             << "of type " << log_type;
-    uploader_->UploadLog(log_store_->staged_json_log(), log_type);
+    uploader_->UploadLog(log_store_->staged_log(), log_type);
   }
 }
 

components/p3a/brave_p3a_service.h

@@ -56,9 +56,8 @@ class BraveP3AService : public base::RefCountedThreadSafe<BraveP3AService>,
       scoped_refptr<network::SharedURLLoaderFactory> url_loader_factory);
 
   // BraveP3ALogStore::Delegate
-  BraveP3ALogStore::LogForJsonMigration Serialize(
-      base::StringPiece histogram_name,
-      uint64_t value) override;
+  std::string Serialize(base::StringPiece histogram_name,
+                        uint64_t value) override;
 
   // May be accessed from multiple threads, so this is thread-safe.
   bool IsActualMetric(base::StringPiece histogram_name) const override;