Match only prefixes of histogram names.

base/test/histogram_tester.cc

Index: base/test/histogram_tester.cc
diff --git a/base/test/histogram_tester.cc b/base/test/histogram_tester.cc
index 90981e232637f8eb3323c96f9f22dc9538c5b89a..59ea1c630217a3e9cdc3d986b8594bc5201db63b 100644
--- a/base/test/histogram_tester.cc
+++ b/base/test/histogram_tester.cc
@@ -11,6 +11,7 @@
 #include "base/metrics/metrics_hashes.h"
 #include "base/metrics/sample_map.h"
 #include "base/metrics/statistics_recorder.h"
+#include "base/strings/string_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
@@ -33,16 +34,14 @@ HistogramTester::~HistogramTester() {
 
 void HistogramTester::ExpectUniqueSample(
     const std::string& name,
-    base::HistogramBase::Sample sample,
-    base::HistogramBase::Count expected_count) const {
-  base::HistogramBase* histogram =
-      base::StatisticsRecorder::FindHistogram(name);
+    HistogramBase::Sample sample,
+    HistogramBase::Count expected_count) const {
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
   EXPECT_NE(nullptr, histogram) << "Histogram \"" << name
                                 << "\" does not exist.";
 
   if (histogram) {
-    std::unique_ptr<base::HistogramSamples> samples =
-        histogram->SnapshotSamples();
+    std::unique_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
     CheckBucketCount(name, sample, expected_count, *samples);
     CheckTotalCount(name, expected_count, *samples);
   }
@@ -50,27 +49,23 @@ void HistogramTester::ExpectUniqueSample(
 
 void HistogramTester::ExpectBucketCount(
     const std::string& name,
-    base::HistogramBase::Sample sample,
-    base::HistogramBase::Count expected_count) const {
-  base::HistogramBase* histogram =
-      base::StatisticsRecorder::FindHistogram(name);
+    HistogramBase::Sample sample,
+    HistogramBase::Count expected_count) const {
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
   EXPECT_NE(nullptr, histogram) << "Histogram \"" << name
                                 << "\" does not exist.";
 
   if (histogram) {
-    std::unique_ptr<base::HistogramSamples> samples =
-        histogram->SnapshotSamples();
+    std::unique_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
     CheckBucketCount(name, sample, expected_count, *samples);
   }
 }
 
 void HistogramTester::ExpectTotalCount(const std::string& name,
-                                       base::HistogramBase::Count count) const {
-  base::HistogramBase* histogram =
-      base::StatisticsRecorder::FindHistogram(name);
+                                       HistogramBase::Count count) const {
+  HistogramBase* histogram = StatisticsRecorder::FindHistogram(name);
   if (histogram) {
-    std::unique_ptr<base::HistogramSamples> samples =
-        histogram->SnapshotSamples();
+    std::unique_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
     CheckTotalCount(name, count, *samples);
   } else {
     // No histogram means there were zero samples.
@@ -78,10 +73,9 @@ void HistogramTester::ExpectTotalCount(const std::string& name,
   }
 }
 
-void HistogramTester::ExpectTimeBucketCount(
-    const std::string& name,
-    base::TimeDelta sample,
-    base::HistogramBase::Count count) const {
+void HistogramTester::ExpectTimeBucketCount(const std::string& name,
+                                            TimeDelta sample,
+                                            HistogramBase::Count count) const {
   ExpectBucketCount(name, sample.InMilliseconds(), count);
 }
 
@@ -102,17 +96,21 @@ std::vector<Bucket> HistogramTester::GetAllSamples(
 }
 
 HistogramTester::CountsMap HistogramTester::GetTotalCountsForPrefix(
-    const std::string& query) const {
-  EXPECT_TRUE(query.find('.') != std::string::npos)
-      << "|query| ought to contain at least one period, to avoid matching too"
+    const std::string& prefix) const {
+  EXPECT_TRUE(prefix.find('.') != std::string::npos)
+      << "|prefix| ought to contain at least one period, to avoid matching too"
       << " many histograms.";
 
-  // Find matches by using the prefix-matching logic built into GetSnapshot().
-  StatisticsRecorder::Histograms query_matches;
-  StatisticsRecorder::GetSnapshot(query, &query_matches);
+  // Find candidate matches by using the logic built into GetSnapshot().
+  StatisticsRecorder::Histograms candidate_matches;
+  StatisticsRecorder::GetSnapshot(prefix, &candidate_matches);
 
   CountsMap result;
-  for (base::HistogramBase* histogram : query_matches) {
+  for (HistogramBase* histogram : candidate_matches) {
+    if (!StartsWith(histogram->histogram_name(), prefix,
+                    CompareCase::SENSITIVE)) {
+      continue;
+    }
     std::unique_ptr<HistogramSamples> new_samples =
         GetHistogramSamplesSinceCreation(histogram->histogram_name());
     // Omit unchanged histograms from the result.
@@ -145,11 +143,10 @@ HistogramTester::GetHistogramSamplesSinceCreation(
   return named_samples;
 }
 
-void HistogramTester::CheckBucketCount(
-    const std::string& name,
-    base::HistogramBase::Sample sample,
-    base::HistogramBase::Count expected_count,
-    const base::HistogramSamples& samples) const {
+void HistogramTester::CheckBucketCount(const std::string& name,
+                                       HistogramBase::Sample sample,
+                                       HistogramBase::Count expected_count,
+                                       const HistogramSamples& samples) const {
   int actual_count = samples.GetCount(sample);
   auto histogram_data = histograms_snapshot_.find(name);
   if (histogram_data != histograms_snapshot_.end())
@@ -162,10 +159,9 @@ void HistogramTester::CheckBucketCount(
       << ").";
 }
 
-void HistogramTester::CheckTotalCount(
-    const std::string& name,
-    base::HistogramBase::Count expected_count,
-    const base::HistogramSamples& samples) const {
+void HistogramTester::CheckTotalCount(const std::string& name,
+                                      HistogramBase::Count expected_count,
+                                      const HistogramSamples& samples) const {
   int actual_count = samples.TotalCount();
   auto histogram_data = histograms_snapshot_.find(name);
   if (histogram_data != histograms_snapshot_.end())