Support "shared" histograms between processes.

base/metrics/statistics_recorder_unittest.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 <vector>
 
 #include "base/bind.h"
 #include "base/json/json_reader.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/metrics/histogram_persistence.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/values.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
 
 class StatisticsRecorderTest : public testing::Test {
  protected:
   void SetUp() override {
     // Each test will have a clean state (no Histogram / BucketRanges
     // registered).
     InitializeStatisticsRecorder();
   }
 
-  void TearDown() override { UninitializeStatisticsRecorder(); }
+  void TearDown() override {
+    UninitializeStatisticsRecorder();
+    SetPersistentHistogramMemoryAllocator(nullptr);
+  }
 
   void InitializeStatisticsRecorder() {
     statistics_recorder_ = new StatisticsRecorder();
   }
 
   void UninitializeStatisticsRecorder() {
     delete statistics_recorder_;
     statistics_recorder_ = NULL;
   }
 
@@ skipping 269 matching lines @@
   EXPECT_EQ("TestHistogram2", histogram_name);
 
   json.clear();
   UninitializeStatisticsRecorder();
 
   // No data should be returned.
   json = StatisticsRecorder::ToJSON(query);
   EXPECT_TRUE(json.empty());
 }
 
+TEST_F(StatisticsRecorderTest, IterationTest) {
+  StatisticsRecorder::Histograms registered_histograms;
+  LOCAL_HISTOGRAM_COUNTS("TestHistogram.IterationTest1", 30);
+  SetPersistentHistogramMemoryAllocator(
+      new LocalPersistentMemoryAllocator(64 << 10, 0, std::string()));
+  LOCAL_HISTOGRAM_COUNTS("TestHistogram.IterationTest2", 30);
+
+  StatisticsRecorder::HistogramIterator i1 = StatisticsRecorder::begin(true);
+  EXPECT_NE(StatisticsRecorder::end(), i1);
+  EXPECT_NE(StatisticsRecorder::end(), ++i1);
+  EXPECT_EQ(StatisticsRecorder::end(), ++i1);
+
+  StatisticsRecorder::HistogramIterator i2 = StatisticsRecorder::begin(false);
+  EXPECT_NE(StatisticsRecorder::end(), i2);
+  EXPECT_EQ(StatisticsRecorder::end(), ++i2);
+}
+
 namespace {
 
 // CallbackCheckWrapper is simply a convenient way to check and store that
 // a callback was actually run.
 struct CallbackCheckWrapper {
   CallbackCheckWrapper() : called(false), last_histogram_value(0) {}
 
   void OnHistogramChanged(base::HistogramBase::Sample histogram_value) {
     called = true;
     last_histogram_value = histogram_value;
@@ skipping 155 matching lines @@
   HistogramBase* histogram = Histogram::FactoryGet("TestHistogram", 1, 1000, 10,
                                                    HistogramBase::kNoFlags);
   EXPECT_TRUE(histogram);
   histogram->Add(1);
 
   EXPECT_TRUE(callback_wrapper.called);
   EXPECT_EQ(callback_wrapper.last_histogram_value, 1);
 }
 
 }  // namespace base