(WIP) Implement V8 Tracing -- DO NOT LAND

gin/event_tracer_impl.h

Index: gin/event_tracer_impl.h
diff --git a/tools/clang/blink_gc_plugin/tests/own_ptr_to_gc_managed_class.cpp b/gin/event_tracer_impl.h
similarity index 58%
copy from tools/clang/blink_gc_plugin/tests/own_ptr_to_gc_managed_class.cpp
copy to gin/event_tracer_impl.h
index 9e27c3d87bc66e8e99bb0144815308d23581d308..3f07e8d09c5715272ddd4021bb3d1f2cce052cdc 100644
--- a/tools/clang/blink_gc_plugin/tests/own_ptr_to_gc_managed_class.cpp
+++ b/gin/event_tracer_impl.h
@@ -2,10 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "own_ptr_to_gc_managed_class.h"
+#ifndef V8_EXT_TRACE_EVENT_H_
+#define V8_EXT_TRACE_EVENT_H_
 
-namespace blink {
 
-void HeapObject::trace(Visitor* visitor) { }
+void InitV8EventTracer();
 
-}
+#endif  // V8_EXT_TRACE_EVENT_H_