Merge multiple histogram snapshots into single one for reporting.

base/metrics/histogram_snapshot_manager_unittest.cc

Index: base/metrics/histogram_snapshot_manager_unittest.cc
diff --git a/base/metrics/histogram_snapshot_manager_unittest.cc b/base/metrics/histogram_snapshot_manager_unittest.cc
index 72db7d58674520206bb96c77e0abc7fffc9a9493..8ec03daa8d97c9579f97dc949c18bfe59c02eb2f 100644
--- a/base/metrics/histogram_snapshot_manager_unittest.cc
+++ b/base/metrics/histogram_snapshot_manager_unittest.cc
@@ -10,7 +10,9 @@
 #include "base/macros.h"
 #include "base/metrics/histogram_delta_serialization.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/metrics/sample_vector.h"
 #include "base/metrics/statistics_recorder.h"
+#include "base/stl_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
@@ -22,6 +24,11 @@ class HistogramFlattenerDeltaRecorder : public HistogramFlattener {
   void RecordDelta(const HistogramBase& histogram,
                    const HistogramSamples& snapshot) override {
     recorded_delta_histogram_names_.push_back(histogram.histogram_name());
+    ASSERT_FALSE(ContainsKey(recorded_delta_histogram_sum_,
+                             histogram.histogram_name()));
+    // Keep pointer to snapshot for testing. This really isn't ideal but the
+    // snapshot-manager keeps the snapshot alive until it's "forgotten".
+    recorded_delta_histogram_sum_[histogram.histogram_name()] = snapshot.sum();
   }
 
   void InconsistencyDetected(HistogramBase::Inconsistency problem) override {
@@ -37,12 +44,23 @@ class HistogramFlattenerDeltaRecorder : public HistogramFlattener {
     ASSERT_TRUE(false);
   }
 
+  void Reset() {
+    recorded_delta_histogram_names_.clear();
+    recorded_delta_histogram_sum_.clear();
+  }
+
   std::vector<std::string> GetRecordedDeltaHistogramNames() {
     return recorded_delta_histogram_names_;
   }
 
+  int64_t GetRecordedDeltaHistogramSum(const std::string& name) {
+    EXPECT_TRUE(ContainsKey(recorded_delta_histogram_sum_, name));
+    return recorded_delta_histogram_sum_[name];
+  }
+
  private:
   std::vector<std::string> recorded_delta_histogram_names_;
+  std::map<std::string, int64_t> recorded_delta_histogram_sum_;
 
   DISALLOW_COPY_AND_ASSIGN(HistogramFlattenerDeltaRecorder);
 };
@@ -61,7 +79,7 @@ class HistogramSnapshotManagerTest : public testing::Test {
 
 TEST_F(HistogramSnapshotManagerTest, PrepareDeltasNoFlagsFilter) {
   // kNoFlags filter should record all histograms.
-  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 2);
+  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 4);
   UMA_STABILITY_HISTOGRAM_ENUMERATION("UmaStabilityHistogram", 1, 2);
 
   histogram_snapshot_manager_.PrepareDeltas(
@@ -77,7 +95,7 @@ TEST_F(HistogramSnapshotManagerTest, PrepareDeltasNoFlagsFilter) {
 
 TEST_F(HistogramSnapshotManagerTest, PrepareDeltasUmaHistogramFlagFilter) {
   // Note that kUmaStabilityHistogramFlag includes kUmaTargetedHistogramFlag.
-  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 2);
+  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 4);
   UMA_STABILITY_HISTOGRAM_ENUMERATION("UmaStabilityHistogram", 1, 2);
 
   histogram_snapshot_manager_.PrepareDeltas(
@@ -93,7 +111,7 @@ TEST_F(HistogramSnapshotManagerTest, PrepareDeltasUmaHistogramFlagFilter) {
 
 TEST_F(HistogramSnapshotManagerTest,
        PrepareDeltasUmaStabilityHistogramFlagFilter) {
-  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 2);
+  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 4);
   UMA_STABILITY_HISTOGRAM_ENUMERATION("UmaStabilityHistogram", 1, 2);
 
   histogram_snapshot_manager_.PrepareDeltas(
@@ -106,4 +124,35 @@ TEST_F(HistogramSnapshotManagerTest,
   EXPECT_EQ("UmaStabilityHistogram", histograms[0]);
 }
 
+TEST_F(HistogramSnapshotManagerTest, CheckMerge) {
+  UMA_HISTOGRAM_ENUMERATION("UmaHistogram", 1, 4);
+  UMA_STABILITY_HISTOGRAM_ENUMERATION("UmaStabilityHistogram", 1, 2);
+
+  base::HistogramBase* h1 = base::LinearHistogram::FactoryGet(
+      "UmaHistogram", 1, 4, 5, 0);
+  ASSERT_TRUE(h1);
+  base::HistogramBase* h2 = base::LinearHistogram::FactoryGet(
+      "UmaStabilityHistogram", 1, 2, 3, 0);
+  ASSERT_TRUE(h2);
+
+  histogram_snapshot_manager_.StartDeltas();
+  histogram_snapshot_manager_.PrepareDelta(h1);
+  histogram_snapshot_manager_.PrepareDelta(h1);  // Delta will be zero.
+  histogram_snapshot_manager_.PrepareDelta(h2);
+  h1->Add(2);
+  h2->Add(1);
+  histogram_snapshot_manager_.PrepareDelta(h2);
+  histogram_snapshot_manager_.PrepareDelta(h1);
+  histogram_snapshot_manager_.FinishDeltas();
+  {
+    const std::vector<std::string> histograms =
+        histogram_flattener_delta_recorder_.GetRecordedDeltaHistogramNames();
+    EXPECT_EQ(2U, histograms.size());
+    EXPECT_EQ(3, histogram_flattener_delta_recorder_.
+                     GetRecordedDeltaHistogramSum("UmaHistogram"));
+    EXPECT_EQ(2, histogram_flattener_delta_recorder_.
+                     GetRecordedDeltaHistogramSum("UmaStabilityHistogram"));
+  }
+}
+
 }  // namespace base