Display histograms from subprocesses in chrome://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 9aafe187be23adef5d1fabaf853d109c13fc0033..d4c903cca4db6639f86da15b6b614ab08b1bc7a6 100644
--- a/base/metrics/statistics_recorder.cc
+++ b/base/metrics/statistics_recorder.cc
@@ -5,6 +5,7 @@
 #include "base/metrics/statistics_recorder.h"
 
 #include <memory>
+#include <set>
 
 #include "base/at_exit.h"
 #include "base/debug/leak_annotations.h"
@@ -29,6 +30,9 @@ bool HistogramNameLesser(const base::HistogramBase* a,
   return a->histogram_name() < b->histogram_name();
 }
 
+base::LazyInstance<std::set<base::StatisticsRecorder::MetricsDisplay*>>::Leaky
+    g_metrics_displays_ = LAZY_INSTANCE_INITIALIZER;
+
 }  // namespace
 
 namespace base {
@@ -203,9 +207,16 @@ void StatisticsRecorder::WriteHTMLGraph(const std::string& query,
   GetSnapshot(query, &snapshot);
   std::sort(snapshot.begin(), snapshot.end(), &HistogramNameLesser);
   for (const HistogramBase* histogram : snapshot) {
-    histogram->WriteHTMLGraph(output);
+    histogram->WriteHTMLGraph(nullptr, output);
     output->append("<br><hr><br>");
   }
+
+  for (auto display : g_metrics_displays_.Get()) {
+    output->append("<hr size=10 noshade><br><hr><br>\n<p>");
+    display->WriteTitleString(output);
+    output->append("</p>\n");
+    display->WriteGraphs(query, true, output);
+  }
 }
 
 // static
@@ -222,9 +233,18 @@ void StatisticsRecorder::WriteGraph(const std::string& query,
   GetSnapshot(query, &snapshot);
   std::sort(snapshot.begin(), snapshot.end(), &HistogramNameLesser);
   for (const HistogramBase* histogram : snapshot) {
-    histogram->WriteAscii(output);
+    histogram->WriteAscii(nullptr, output);
     output->append("\n");
   }
+
+  for (auto display : g_metrics_displays_.Get()) {
+    output->append(
+        "########################################"
+        "########################################\n\n");
+    display->WriteTitleString(output);
+    output->append("\n\n");
+    display->WriteGraphs(query, false, output);
+  }
 }
 
 // static
@@ -401,6 +421,18 @@ size_t StatisticsRecorder::GetHistogramCount() {
 }
 
 // static
+void StatisticsRecorder::RegisterMetricsDisplay(MetricsDisplay* display) {
+  DCHECK(!ContainsKey(g_metrics_displays_.Get(), display));
+  g_metrics_displays_.Get().insert(display);
+}
+
+// static
+void StatisticsRecorder::DeregisterMetricsDisplay(MetricsDisplay* display) {
+  DCHECK(ContainsKey(g_metrics_displays_.Get(), display));
+  g_metrics_displays_.Get().erase(display);
+}
+
+// static
 void StatisticsRecorder::ForgetHistogramForTesting(base::StringPiece name) {
   if (histograms_)
     histograms_->erase(name);