NetworkQualityEstimator: Enable prefs writing by default

chrome/browser/net/nqe/ui_network_quality_estimator_service.cc

 // Copyright 2016 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 "chrome/browser/net/nqe/ui_network_quality_estimator_service.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
@@ skipping 25 matching lines @@
 
   const auto it = network_quality_estimator_params.find(parameter_name);
   return it == network_quality_estimator_params.end() ? default_value
                                                       : it->second;
 }
 
 // Returns true if writing to the persistent cache has been enabled via field
 // trial.
 bool persistent_cache_writing_enabled() {
   return GetStringValueForVariationParamWithDefaultValue(
-             "persistent_cache_writing_enabled", "false") == "true";
+             "persistent_cache_writing_enabled", "true") == "true";
 }
 
 // Returns true if reading from the persistent cache has been enabled via field
 // trial.
 bool persistent_cache_reading_enabled() {
-  return GetStringValueForVariationParamWithDefaultValue(
-             "persistent_cache_reading_enabled", "false") == "true";
+  if (GetStringValueForVariationParamWithDefaultValue(
+          "persistent_cache_reading_enabled", "false") != "true") {
+    return false;
+  }
+  // If reading from prefs is enabled, then writing to prefs must be enabled
+  // too.
+  DCHECK(persistent_cache_writing_enabled());
+  return true;
 }
 
 // PrefDelegateImpl writes the provided dictionary value to the network quality
 // estimator prefs on the disk.
 class PrefDelegateImpl
     : public net::NetworkQualitiesPrefsManager::PrefDelegate {
  public:
   // |pref_service| is used to read and write prefs from/to the disk.
   explicit PrefDelegateImpl(PrefService* pref_service)
       : pref_service_(pref_service), path_(prefs::kNetworkQualities) {
     DCHECK(pref_service_);
   }
   ~PrefDelegateImpl() override {}
 
   void SetDictionaryValue(const base::DictionaryValue& value) override {
     DCHECK(thread_checker_.CalledOnValidThread());
     if (!persistent_cache_writing_enabled())
       return;
 
     pref_service_->Set(path_, value);
-    UMA_HISTOGRAM_COUNTS_1000("NQE.Prefs.WriteCount", 1);
+    UMA_HISTOGRAM_EXACT_LINEAR("NQE.Prefs.WriteCount", 1, 2);
   }
 
   std::unique_ptr<base::DictionaryValue> GetDictionaryValue() override {
     DCHECK(thread_checker_.CalledOnValidThread());
     if (!persistent_cache_reading_enabled())
       return base::WrapUnique(new base::DictionaryValue());
-    UMA_HISTOGRAM_COUNTS_1000("NQE.Prefs.ReadCount", 1);
+    UMA_HISTOGRAM_EXACT_LINEAR("NQE.Prefs.ReadCount", 1, 2);
     return pref_service_->GetDictionary(path_)->CreateDeepCopy();
   }
 
  private:
   PrefService* pref_service_;
 
   // |path_| is the location of the network quality estimator prefs.
   const std::string path_;
 
   base::ThreadChecker thread_checker_;
@@ skipping 184 matching lines @@
 
 std::map<net::nqe::internal::NetworkID,
          net::nqe::internal::CachedNetworkQuality>
 UINetworkQualityEstimatorService::ForceReadPrefsForTesting() const {
   if (!prefs_manager_) {
     return std::map<net::nqe::internal::NetworkID,
                     net::nqe::internal::CachedNetworkQuality>();
   }
   return prefs_manager_->ForceReadPrefsForTesting();
 }