Add a switch to emit browser histograms.

BUG=None

Review URL: https://codereview.chromium.org/61983003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235191 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 102 insertions, 3 deletions

diff --git a/base/metrics/statistics_recorder.cc b/base/metrics/statistics_recorder.cc
index f23c810..1e28fbe 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -6,11 +6,13 @@
 
 #include "base/at_exit.h"
 #include "base/debug/leak_annotations.h"
+#include "base/json/string_escape.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/lock.h"
+#include "base/values.h"
 
 using std::list;
 using std::string;
@@ -163,6 +165,37 @@ void StatisticsRecorder::WriteGraph(const std::string& query,
 }
 
 // static
+std::string StatisticsRecorder::ToJSON(const std::string& query) {
+  if (!IsActive())
+    return std::string();
+
+  std::string output("{");
+  if (!query.empty()) {
+    output += "\"query\":";
+    JsonDoubleQuote(query, true, &output);
+    output += ",";
+  }
+
+  Histograms snapshot;
+  GetSnapshot(query, &snapshot);
+  output += "\"histograms\":[";
+  std::string json;
+  bool first_histogram = true;
+  for (Histograms::const_iterator it = snapshot.begin(); it != snapshot.end();
+       ++it) {
+    if (first_histogram)
+      first_histogram = false;
+    else
+      output += ",";
+    json.clear();
+    (*it)->WriteJSON(&json);
+    output += json;
+  }
+  output += "]}";
+  return output;
+}
+
+// static
 void StatisticsRecorder::GetHistograms(Histograms* output) {
   if (lock_ == NULL)
     return;
diff --git a/base/metrics/statistics_recorder.h b/base/metrics/statistics_recorder.h
index 0fdfb76..0716e80 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -49,12 +49,16 @@ class BASE_EXPORT StatisticsRecorder {
   static const BucketRanges* RegisterOrDeleteDuplicateRanges(
       const BucketRanges* ranges);
 
-  // Methods for printing histograms.  Only histograms which have query as
-  // a substring are written to output (an empty string will process all
-  // registered histograms).
+  // Methods for appending histogram data to a string.  Only histograms which
+  // have |query| as a substring are written to |output| (an empty string will
+  // process all registered histograms).
   static void WriteHTMLGraph(const std::string& query, std::string* output);
   static void WriteGraph(const std::string& query, std::string* output);
 
+  // Returns the histograms with |query| as a substring as JSON text (an empty
+  // |query| will process all registered histograms).
+  static std::string ToJSON(const std::string& query);
+
   // Method for extracting histograms which were marked for use by UMA.
   static void GetHistograms(Histograms* output);
 
diff --git a/base/metrics/statistics_recorder_unittest.cc b/base/metrics/statistics_recorder_unittest.cc
index 22504dd..906e642 100644
--- a/base/metrics/statistics_recorder_unittest.cc
+++ b/base/metrics/statistics_recorder_unittest.cc
@@ -4,9 +4,11 @@
 
 #include <vector>
 
+#include "base/json/json_reader.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/statistics_recorder.h"
+#include "base/values.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace base {
@@ -263,4 +265,64 @@ TEST_F(StatisticsRecorderTest, BucketRangesSharing) {
   EXPECT_EQ(2u, ranges.size());
 }
 
+TEST_F(StatisticsRecorderTest, ToJSON) {
+  HISTOGRAM_COUNTS("TestHistogram1", 30);
+  HISTOGRAM_COUNTS("TestHistogram1", 40);
+  HISTOGRAM_COUNTS("TestHistogram2", 30);
+  HISTOGRAM_COUNTS("TestHistogram2", 40);
+
+  std::string json(StatisticsRecorder::ToJSON(std::string()));
+
+  // Check for valid JSON.
+  scoped_ptr<Value> root;
+  root.reset(JSONReader::Read(json));
+  ASSERT_TRUE(root.get());
+
+  DictionaryValue* root_dict = NULL;
+  ASSERT_TRUE(root->GetAsDictionary(&root_dict));
+
+  // No query should be set.
+  ASSERT_FALSE(root_dict->HasKey("query"));
+
+  ListValue* histogram_list = NULL;
+  ASSERT_TRUE(root_dict->GetList("histograms", &histogram_list));
+  ASSERT_EQ(2u, histogram_list->GetSize());
+
+  // Examine the first histogram.
+  DictionaryValue* histogram_dict = NULL;
+  ASSERT_TRUE(histogram_list->GetDictionary(0, &histogram_dict));
+
+  int sample_count;
+  ASSERT_TRUE(histogram_dict->GetInteger("count", &sample_count));
+  EXPECT_EQ(2, sample_count);
+
+  // Test the query filter.
+  std::string query("TestHistogram2");
+  json = StatisticsRecorder::ToJSON(query);
+
+  root.reset(JSONReader::Read(json));
+  ASSERT_TRUE(root.get());
+  ASSERT_TRUE(root->GetAsDictionary(&root_dict));
+
+  std::string query_value;
+  ASSERT_TRUE(root_dict->GetString("query", &query_value));
+  EXPECT_EQ(query, query_value);
+
+  ASSERT_TRUE(root_dict->GetList("histograms", &histogram_list));
+  ASSERT_EQ(1u, histogram_list->GetSize());
+
+  ASSERT_TRUE(histogram_list->GetDictionary(0, &histogram_dict));
+
+  std::string histogram_name;
+  ASSERT_TRUE(histogram_dict->GetString("name", &histogram_name));
+  EXPECT_EQ("TestHistogram2", histogram_name);
+
+  json.clear();
+  UninitializeStatisticsRecorder();
+
+  // No data should be returned.
+  json = StatisticsRecorder::ToJSON(query);
+  EXPECT_TRUE(json.empty());
+}
+
 }  // namespace base