[Telemetry] Add support for capturing V8 object stats to Telemetry.

content/renderer/stats_collection_controller.cc

Index: content/renderer/stats_collection_controller.cc
diff --git a/content/renderer/stats_collection_controller.cc b/content/renderer/stats_collection_controller.cc
index f82a8c4fd561450070e0213981551881d19e315c..9c9bf608c5a3b33416f34a27a95b211f6573f997 100644
--- a/content/renderer/stats_collection_controller.cc
+++ b/content/renderer/stats_collection_controller.cc
@@ -9,6 +9,7 @@
 #include "base/json/json_writer.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/statistics_recorder.h"
+#include "base/metrics/stats_table.h"
 #include "base/strings/string_util.h"
 #include "content/common/child_process_messages.h"
 #include "content/renderer/render_view_impl.h"
@@ -73,6 +74,34 @@ void ConvertLoadTimeToJSON(
   base::JSONWriter::Write(&item, result);
 }
 
+
+// Encodes StatsTable as json.
+// - |stats_table| - StatsTable to encode.
+// - |pid| - The process id to get stats for (0 for all processes).
+// - |result| - returned JSON.
+// Example return value:
+// {'c:V8:TotalEvalSize': 102664, 'c:V8:TotalLoadSize': 164356}
+void ConvertStatsTableToJSON(
+    const base::StatsTable* stats_table,
+    const base::ProcessId pid,
+    std::string *result) {
+  base::DictionaryValue counters;
+  // NOTE: Counters start at index 1.
+  for (int index = 1; index <= stats_table->GetMaxCounters(); index++) {
+    std::string name = stats_table->GetRowName(index);
+    if (name.length() == 0)
+      break;
+
+    // JSON doesn't allow '.' in names.
+    size_t pos;
+    while ((pos = name.find(".")) != std::string::npos)
+      name.replace(pos, 1, ":");
+
+    counters.SetInteger(name, stats_table->GetRowValue(index, pid));
+  }
+  base::JSONWriter::Write(&counters, result);
+}
+
 }  // namespace
 
 StatsCollectionController::StatsCollectionController()
@@ -83,6 +112,10 @@ StatsCollectionController::StatsCollectionController()
   BindCallback("getBrowserHistogram",
                base::Bind(&StatsCollectionController::GetBrowserHistogram,
                           base::Unretained(this)));
+  BindCallback("getStatsTable",
+               base::Bind(
+                  &StatsCollectionController::GetStatsTable,
+                  base::Unretained(this)));
   BindCallback("tabLoadTiming",
                base::Bind(
                   &StatsCollectionController::GetTabLoadTiming,
@@ -90,7 +123,7 @@ StatsCollectionController::StatsCollectionController()
 }
 
 void StatsCollectionController::GetHistogram(const CppArgumentList& args,
-                                            CppVariant* result) {
+                                             CppVariant* result) {
   if (args.size() != 1) {
     result->SetNull();
     return;
@@ -107,7 +140,7 @@ void StatsCollectionController::GetHistogram(const CppArgumentList& args,
 }
 
 void StatsCollectionController::GetBrowserHistogram(const CppArgumentList& args,
-                                                   CppVariant* result) {
+                                                    CppVariant* result) {
   if (args.size() != 1) {
     result->SetNull();
     return;
@@ -125,6 +158,18 @@ void StatsCollectionController::GetBrowserHistogram(const CppArgumentList& args,
   result->Set(histogram_json);
 }
 
+void StatsCollectionController::GetStatsTable(const CppArgumentList& args,
+                                              CppVariant* result) {
+  base::StatsTable* stats_table = base::StatsTable::current();
+  std::string output;
+  if (!stats_table) {
+    output = "{}";
+  } else {
+    ConvertStatsTableToJSON(stats_table, base::GetCurrentProcId(), &output);
+  }
+  result->Set(output);
+}
+
 void StatsCollectionController::GetTabLoadTiming(
     const CppArgumentList& args,
     CppVariant* result) {