Add a switch to emit browser histograms.

base/metrics/statistics_recorder.cc

Index: base/metrics/statistics_recorder.cc
diff --git a/base/metrics/statistics_recorder.cc b/base/metrics/statistics_recorder.cc
index f23c81054cf5cff26915da0ae36ffd34f9e69050..e75857b41a969e1882339425bb987b2bc63ef22e 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
+void StatisticsRecorder::WriteJSON(const std::string& query,
+                                   std::string* output) {
+  if (!IsActive())
+    return;
+
+  *output = "{";
+  if (query.length()) {
+    output->append("\"query\":");
+    JsonDoubleQuote(query, true, output);
+    output->append(",");
+  }
+
+  Histograms snapshot;
+  GetSnapshot(query, &snapshot);
+  output->append("\"histograms\":[");
+  std::string json;
+  bool first_time = true;
+  for (Histograms::const_iterator it = snapshot.begin(); it != snapshot.end();
+       ++it) {
+    if (first_time)
+      first_time = false;
+    else
+      output->append(",");
+    json.clear();
+    (*it)->WriteJSON(&json);
+    output->append(json);
+  }
+  output->append("]}");
+}
+
+// static
 void StatisticsRecorder::GetHistograms(Histograms* output) {
   if (lock_ == NULL)
     return;