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 4eecddade8058c723392abb32152778e3c5c59eb..65c67ce7fe44eb87eb3c8768459b4232f6f56563 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::MetricsDisplayer*>>::Leaky
+    g_metrics_displayers_ = LAZY_INSTANCE_INITIALIZER;

[Ilya Sherman, 2016/04/25 20:53:14]

Rather than introducing an additional global object, could the metrics
displayers be owned by the StatisticsRecorder?

[bcwhite, 2016/04/26 19:51:53]

Yes.  That'll mean including lazy_instance.h in the statistics_recorder.h file. 
Alexei has generally preferred globals over statics when something is completely
internal.

[Ilya Sherman, 2016/04/26 20:21:58]

Why would it need to be a lazy instance (or static, for that matter) if it's
internal to the class?

[bcwhite, 2016/04/26 21:03:29]

Calls to this method are made as MetricsDisplayer objects are created which
could be any time.  A lazy-initializer always works regardless of when.

But I think it would be safe to ceate the object inside
Statistics::Recorder::Initialize().  I doubt any MetricsDisplayer objects would
be created before that call.

+
 }  // namespace
 
 namespace base {
@@ -211,9 +215,16 @@ 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_displayers_.Get()) {
+    output->append("<hr size=10 noshade><br><hr><br>\n<p>");
+    display->WriteTitleString(output);
+    output->append("</p>\n");
+    display->WriteGraphs(query, MetricsDisplayer::DISPLAY_TEXT_HTML, output);
+  }
 }
 
 // static
@@ -230,9 +241,18 @@ 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_displayers_.Get()) {
+    output->append(
+        "########################################"
+        "########################################\n\n");
+    display->WriteTitleString(output);
+    output->append("\n\n");
+    display->WriteGraphs(query, MetricsDisplayer::DISPLAY_TEXT_PLAIN, output);
+  }
 }
 
 // static
@@ -415,6 +435,18 @@ size_t StatisticsRecorder::GetHistogramCount() {
 }
 
 // static
+void StatisticsRecorder::RegisterMetricsDisplayer(MetricsDisplayer* display) {
+  DCHECK(!ContainsKey(g_metrics_displayers_.Get(), display));
+  g_metrics_displayers_.Get().insert(display);
+}
+
+// static
+void StatisticsRecorder::DeregisterMetricsDisplayer(MetricsDisplayer* display) {
+  DCHECK(ContainsKey(g_metrics_displayers_.Get(), display));
+  g_metrics_displayers_.Get().erase(display);
+}
+
+// static
 void StatisticsRecorder::ForgetHistogramForTesting(base::StringPiece name) {
   if (histograms_)
     histograms_->erase(name);