Add a switch to emit browser histograms.

base/metrics/statistics_recorder.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 "base/metrics/statistics_recorder.h"
 
 #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;
 
 namespace {
 // Initialize histogram statistics gathering system.
 base::LazyInstance<base::StatisticsRecorder>::Leaky g_statistics_recorder_ =
     LAZY_INSTANCE_INITIALIZER;
 }  // namespace
 
@@ skipping 132 matching lines @@
   GetSnapshot(query, &snapshot);
   for (Histograms::iterator it = snapshot.begin();
        it != snapshot.end();
        ++it) {
     (*it)->WriteAscii(output);
     output->append("\n");
   }
 }
 
 // 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;
   base::AutoLock auto_lock(*lock_);
   if (histograms_ == NULL)
     return;
 
   for (HistogramMap::iterator it = histograms_->begin();
        histograms_->end() != it;
        ++it) {
@@ skipping 107 matching lines @@
 
 
 // static
 StatisticsRecorder::HistogramMap* StatisticsRecorder::histograms_ = NULL;
 // static
 StatisticsRecorder::RangesMap* StatisticsRecorder::ranges_ = NULL;
 // static
 base::Lock* StatisticsRecorder::lock_ = NULL;
 
 }  // namespace base