Implement tracing interface for v8

src/tracing/event-tracer.cc

Index: src/tracing/event-tracer.cc
diff --git a/src/tracing/event-tracer.cc b/src/tracing/event-tracer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..48163a76fee1f714354805c7f5c2235939552c50
--- /dev/null
+++ b/src/tracing/event-tracer.cc
@@ -0,0 +1,54 @@
+// Copyright 2015 the V8 project 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 <include/v8-tracing.h>
+
+#include "src/log.h"
+#include "src/v8.h"
+
+class DefaultEventTracer : public v8::EventTracer {
+  virtual v8::EventTracer::Handle AddTraceEvent(
+      char phase, const uint8_t* categoryEnabledFlag, const char* name,
+      uint64_t id, uint64_t context_id, uint64_t bind_id, int numArgs,
+      const char** argNames, const uint8_t* argTypes, const uint64_t* argValues,
+      unsigned int flags) {
+    return 0;
+  }
+
+  virtual void UpdateTraceEventDuration(const uint8_t* categoryEnabledFlag,
+                                        const char* name,
+                                        EventTracer::Handle handle) {}
+
+  virtual const uint8_t* GetCategoryGroupEnabled(const char* name) {
+    static uint8_t no = 0;
+    return &no;
+  }
+
+  virtual const char* GetCategoryGroupName(const uint8_t* categoryEnabledFlag) {
+    static const char* dummy = "dummy";
+    return dummy;
+  }
+};
+
+
+static void CleanupTracer() {
+  // calling SetInstance will delete the existing instance.
+  v8::EventTracer::SetInstance(NULL);
+}
+
+
+static void IntializeDefaultTracer(v8::EventTracer* current_instance) {
+  if (current_instance == NULL)
+    v8::EventTracer::SetInstance(new (DefaultEventTracer));
+  atexit(CleanupTracer);
+}
+
+
+V8_DECLARE_ONCE(init_once);
+v8::EventTracer* v8::EventTracer::instance;
+v8::EventTracer* v8::EventTracer::GetInstance() {
+  base::CallOnce(&init_once, IntializeDefaultTracer, v8::EventTracer::instance);
+  DCHECK(v8::EventTracer::instance);
+  return v8::EventTracer::instance;
+}