base/test/histogram_tester.h: Add a way to query a whole family of related

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 ea738b0557b6e864a7e68c7d840c079d5c5967d8..3ca7515b1046c94d50a238962a125bad434c6513 100644
--- a/base/test/histogram_tester.cc
+++ b/base/test/histogram_tester.cc
@@ -4,10 +4,15 @@
 
 #include "base/test/histogram_tester.h"
 
+#include <algorithm>
+#include <vector>
+
 #include "base/metrics/histogram.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/stl_util.h"
+#include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
@@ -73,6 +78,45 @@ void HistogramTester::ExpectTotalCount(const std::string& name,
   }
 }
 
+std::string HistogramTester::GetTotalCountsForQuery(
+    const std::string& query) const {
+  EXPECT_TRUE(query.find('.') != std::string::npos)
+      << "|query| ought to contain at least one period, to avoid matching too"
+      << " many histograms.";

[Ilya Sherman, 2015/06/23 00:57:40]

nit: Perhaps output the query?

+
+  std::vector<std::string> result;
+  StatisticsRecorder::Histograms histograms;
+  StatisticsRecorder::GetSnapshot(query, &histograms);
+  for (base::HistogramBase* histogram : histograms) {
+    scoped_ptr<HistogramSamples> samples = histogram->SnapshotSamples();
+    auto old_histogram = histograms_snapshot_.find(histogram->histogram_name());
+    if (old_histogram != histograms_snapshot_.end())
+      samples->Subtract(*old_histogram->second);
+
+    if (histogram->GetHistogramType() == LINEAR_HISTOGRAM ||
+        histogram->GetHistogramType() == BOOLEAN_HISTOGRAM) {
+      for (scoped_ptr<SampleCountIterator> bucket_it = samples->Iterator();
+           !bucket_it->Done(); bucket_it->Next()) {
+        HistogramBase::Sample min, max;
+        HistogramBase::Count count;
+        bucket_it->Get(&min, &max, &count);
+        if (count != 0) {
+          result.push_back(base::StringPrintf(
+              "%s[%d]=%d", histogram->histogram_name().c_str(), min, count));
+        }
+      }
+    } else {
+      HistogramBase::Count count = samples->TotalCount();
+      if (count != 0) {
+        result.push_back(base::StringPrintf(
+            "%s=%d", histogram->histogram_name().c_str(), count));
+      }
+    }
+  }
+  std::sort(result.begin(), result.end());
+  return JoinString(result, "\n");
+}
+
 scoped_ptr<HistogramSamples> HistogramTester::GetHistogramSamplesSinceCreation(
     const std::string& histogram_name) {
   HistogramBase* histogram = StatisticsRecorder::FindHistogram(histogram_name);