NQE: Use cached estimates

net/nqe/network_qualities_prefs_manager_unittest.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 "net/nqe/network_qualities_prefs_manager.h"
 
 #include <map>
 #include <memory>
 
 #include "base/macros.h"
 #include "base/run_loop.h"
+#include "base/test/histogram_tester.h"
 #include "base/threading/thread_checker.h"
 #include "base/values.h"
 #include "net/base/network_change_notifier.h"
 #include "net/nqe/effective_connection_type.h"
 #include "net/nqe/network_quality_estimator_test_util.h"
 #include "net/nqe/network_quality_store.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace net {
 
@@ skipping 11 matching lines @@
   }
 
   void SetDictionaryValue(const base::DictionaryValue& value) override {
     DCHECK(thread_checker_.CalledOnValidThread());
 
     write_count_++;
     value_.reset(value.DeepCopy());
     ASSERT_EQ(value.size(), value_->size());
   }
 
-  const base::DictionaryValue& GetDictionaryValue() override {
+  std::unique_ptr<base::DictionaryValue> GetDictionaryValue() override {
     DCHECK(thread_checker_.CalledOnValidThread());
 
     read_count_++;
-    return *(value_.get());
+    return value_->CreateDeepCopy();
   }
 
   size_t write_count() const {
     DCHECK(thread_checker_.CalledOnValidThread());
     return write_count_;
   }
 
   size_t read_count() const {
     DCHECK(thread_checker_.CalledOnValidThread());
     return read_count_;
@@ skipping 160 matching lines @@
                   it->second.effective_connection_type());
         break;
       case NetworkChangeNotifier::ConnectionType::CONNECTION_WIFI:
         EXPECT_EQ(EFFECTIVE_CONNECTION_TYPE_SLOW_2G,
                   it->second.effective_connection_type());
         break;
       default:
         NOTREACHED();
     }
   }
+
+  base::HistogramTester histogram_tester;
+  estimator.OnPrefsRead(read_prefs);
+  histogram_tester.ExpectUniqueSample("NQE.Prefs.ReadSize", 3, 1);
+
   manager.ShutdownOnPrefThread();
 }
 
 // Verifies that the prefs are cleared correctly.
 TEST(NetworkQualitiesPrefManager, ClearPrefs) {
   std::map<std::string, std::string> variation_params;
   TestNetworkQualityEstimator estimator(variation_params, nullptr);
 
   std::unique_ptr<TestPrefDelegate> prefs_delegate(new TestPrefDelegate());
 
@@ skipping 26 matching lines @@
   base::RunLoop().RunUntilIdle();
   // Verify that the observer was notified, and the updated network quality was
   // written to the prefs.
   EXPECT_EQ(1u, manager.ForceReadPrefsForTesting().size());
   manager.ShutdownOnPrefThread();
 }
 
 }  // namespace
 
 }  // namespace net