Oilpan: have PendingScripts trace their script elements.

Source/core/dom/PendingScript.cpp

Index: Source/core/dom/PendingScript.cpp
diff --git a/Source/core/dom/PendingScript.cpp b/Source/core/dom/PendingScript.cpp
index b448c8bd9bfd823a5d7255426a9dcd745171bb04..ec5e7a09d521081e58920ac22050f796dac6df5a 100644
--- a/Source/core/dom/PendingScript.cpp
+++ b/Source/core/dom/PendingScript.cpp
@@ -35,7 +35,7 @@ PendingScript::~PendingScript()
 {
 }
 
-PassRefPtr<Element> PendingScript::releaseElementAndClear()
+PassRefPtrWillBeRawPtr<Element> PendingScript::releaseElementAndClear()
 {
     setScriptResource(0);
     m_watchingForLoad = false;
@@ -52,4 +52,20 @@ void PendingScript::notifyFinished(Resource*)
 {
 }
 
+void PendingScript::trace(Visitor* visitor)
+{
+    // FIXME: Oilpan: this trace() is for a PendingScript that's not
+    // on the heap -- it is kept by script runner objects
+    // (ScriptRunner and HTMLScriptRunner), which are OwnPtr-kept by
+    // the document and the HTML document parser, respectively. The
+    // reason they are OwnPtrs and not on the heap themselves, is due
+    // to their need to finalize by using their hosts -- something
+    // that's not readily doable if both host and script runner object
+    // are heap allocated.
+    //
+    // Find a better arrangment, or at least clarify that this is the
+    // most practical way to handle such a dependency.
+    visitor->trace(m_element);
+}
+
 }