Let Dart code running in Sky add events to the trace timeline

sky/engine/core/frame/Tracing.cpp

Index: sky/engine/core/frame/Tracing.cpp
diff --git a/sky/engine/core/frame/Tracing.cpp b/sky/engine/core/frame/Tracing.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..3359da2abb77fc51d02999922bd1cf9c567341a1
--- /dev/null
+++ b/sky/engine/core/frame/Tracing.cpp
@@ -0,0 +1,33 @@
+// Copyright 2015 The Chromium 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 "sky/engine/config.h"
+#include "sky/engine/core/frame/Tracing.h"
+
+#include "base/trace_event/trace_event.h"
+#include "sky/engine/wtf/text/StringUTF8Adaptor.h"
+
+namespace blink {
+
+Tracing::Tracing()
+{
+}
+
+Tracing::~Tracing()
+{
+}
+
+void Tracing::begin(const String& name)
+{
+    StringUTF8Adaptor utf8(name);
+    TRACE_EVENT_COPY_BEGIN0("script", utf8.data());
+}
+
+void Tracing::end(const String& name)
+{
+    StringUTF8Adaptor utf8(name);
+    TRACE_EVENT_COPY_END0("script", utf8.data());
+}
+
+} // namespace blink