win: Make oilpan plugin work better with delayed template parsing.

tools/clang/blink_gc_plugin/tests/delayed_parsing.cpp

+#include "heap/stubs.h"
+
+namespace blink {
+
+struct HeapObject : public GarbageCollected<HeapObject> {
+    void trace(Visitor*) { }
+};
+
+template<typename T>
+class TemplateBase
+    : public GarbageCollected<TemplateBase<T> > {
+public:
+    void trace(Visitor* visitor) { visitor->trace(m_obj); }
+private:
+    Member<HeapObject> m_obj;
+};
+
+class Subclass : public TemplateBase<Subclass> {
+};
+
+}