Introduce infrastructure for tracing ScriptWrappables.

third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp

Index: third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp b/third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp
index 437bf83932da2186d80e05737591d455cae89909..fe1e2109876e1a32ed618ffe409fb4c65694ac2f 100644
--- a/third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/ActiveScriptWrappable.cpp
@@ -4,6 +4,7 @@
 
 #include "bindings/core/v8/ActiveScriptWrappable.h"
 
+#include "bindings/core/v8/ScriptWrappable.h"
 #include "wtf/HashSet.h"
 #include "wtf/ThreadSpecific.h"
 #include "wtf/Threading.h"
@@ -38,4 +39,14 @@ ScriptWrappable* ActiveScriptWrappable::toScriptWrappable() const
     return m_scriptWrappable;
 }
 
+void ActiveScriptWrappable::traceActiveScriptWrappables(ScriptWrappableVisitor* visitor)
+{
+    for (auto activeWrappable : activeScriptWrappables()) {
+        if (!activeWrappable->hasPendingActivity())
+            continue;
+
+        visitor->traceWrappers(activeWrappable->toScriptWrappable());
+    }
+}
+
 } // namespace blink