Log pref file size histogram on read rather than on write.

base/prefs/json_pref_store.cc

 // Copyright (c) 2012 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.
 
 #include "base/prefs/json_pref_store.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 73 matching lines @@
         base::Move(path, bad);
         return bad_existed ? PersistentPrefStore::PREF_READ_ERROR_JSON_REPEAT
                            : PersistentPrefStore::PREF_READ_ERROR_JSON_PARSE;
     }
   } else if (!value->IsType(base::Value::TYPE_DICTIONARY)) {
     return PersistentPrefStore::PREF_READ_ERROR_JSON_TYPE;
   }
   return PersistentPrefStore::PREF_READ_ERROR_NONE;
 }
 
+// Records a sample for |size| in the Settings.JsonDataReadSizeKilobytes
+// histogram suffixed with the base name of the JSON file under |path|.
+void RecordJsonDataSizeHistogram(const base::FilePath& path, size_t size) {
+  std::string spaceless_basename;
+  base::ReplaceChars(path.BaseName().MaybeAsASCII(), " ", "_",
+                     &spaceless_basename);
+
+  // The histogram below is an expansion of the UMA_HISTOGRAM_CUSTOM_COUNTS
+  // macro adapted to allow for a dynamically suffixed histogram name.
+  // Note: The factory creates and owns the histogram.
+  base::HistogramBase* histogram = base::Histogram::FactoryGet(
+      "Settings.JsonDataReadSizeKilobytes." + spaceless_basename, 1, 10000, 50,
+      base::HistogramBase::kUmaTargetedHistogramFlag);
+  histogram->Add(static_cast<int>(size) / 1024);
+}
+
 scoped_ptr<JsonPrefStore::ReadResult> ReadPrefsFromDisk(
     const base::FilePath& path,
     const base::FilePath& alternate_path) {
   if (!base::PathExists(path) && !alternate_path.empty() &&
       base::PathExists(alternate_path)) {
     base::Move(alternate_path, path);
   }
 
   int error_code;
   std::string error_msg;
   scoped_ptr<JsonPrefStore::ReadResult> read_result(
       new JsonPrefStore::ReadResult);
   JSONFileValueSerializer serializer(path);
   read_result->value.reset(serializer.Deserialize(&error_code, &error_msg));
   read_result->error =
       HandleReadErrors(read_result->value.get(), path, error_code, error_msg);
   read_result->no_dir = !base::PathExists(path.DirName());
+
+  if (read_result->error == PersistentPrefStore::PREF_READ_ERROR_NONE)
+    RecordJsonDataSizeHistogram(path, serializer.get_last_read_size());
+
   return read_result.Pass();
 }
 
 }  // namespace
 
 // static
 scoped_refptr<base::SequencedTaskRunner> JsonPrefStore::GetTaskRunnerForFile(
     const base::FilePath& filename,
     base::SequencedWorkerPool* worker_pool) {
   std::string token("json_pref_store-");
@@ skipping 251 matching lines @@
 }
 
 bool JsonPrefStore::SerializeData(std::string* output) {
   DCHECK(CalledOnValidThread());
 
   if (pref_filter_)
     pref_filter_->FilterSerializeData(prefs_.get());
 
   JSONStringValueSerializer serializer(output);
   serializer.set_pretty_print(true);
-  bool result = serializer.Serialize(*prefs_);
-
-  if (result) {
-    std::string spaceless_basename;
-    base::ReplaceChars(path_.BaseName().MaybeAsASCII(), " ", "_",
-                       &spaceless_basename);
-
-    // The histogram below is an expansion of the UMA_HISTOGRAM_COUNTS_10000
-    // macro adapted to allow for a dynamically suffixed histogram name.
-    // Note: The factory creates and owns the histogram.
-    base::HistogramBase* histogram =
-        base::LinearHistogram::FactoryGet(
-            "Settings.JsonDataSizeKilobytes." + spaceless_basename,
-            1,
-            10000,
-            50,
-            base::HistogramBase::kUmaTargetedHistogramFlag);
-    histogram->Add(static_cast<int>(output->size()) / 1024);
-  }
-
-  return result;
+  return serializer.Serialize(*prefs_);
 }
 
 void JsonPrefStore::FinalizeFileRead(bool initialization_successful,
                                      scoped_ptr<base::DictionaryValue> prefs,
                                      bool schedule_write) {
   DCHECK(CalledOnValidThread());
 
   filtering_in_progress_ = false;
 
   if (!initialization_successful) {
@@ skipping 12 matching lines @@
 
   if (error_delegate_ && read_error_ != PREF_READ_ERROR_NONE)
     error_delegate_->OnError(read_error_);
 
   FOR_EACH_OBSERVER(PrefStore::Observer,
                     observers_,
                     OnInitializationCompleted(true));
 
   return;
 }