blink_gc_plugin: retire overloaded traceImpl detection and handling.

tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded.cpp

Index: tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded.cpp
diff --git a/tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded.cpp b/tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded.cpp
index 02d485835187d56e27c108228a7f63548dc5d583..dc7051cd1aa69bd5ed8ae5adc0ad0d5db17103f0 100644
--- a/tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded.cpp
+++ b/tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded.cpp
@@ -7,28 +7,10 @@
 namespace blink {
 
 void ExternBase::trace(Visitor* visitor) {
-  traceImpl(visitor);
-}
-
-void ExternBase::trace(InlinedGlobalMarkingVisitor visitor) {
-  traceImpl(visitor);
-}
-
-template <typename VisitorDispatcher>
-inline void ExternBase::traceImpl(VisitorDispatcher visitor) {
   visitor->trace(x_base_);
 }
 
 void ExternDerived::trace(Visitor* visitor) {
-  traceImpl(visitor);
-}
-
-void ExternDerived::trace(InlinedGlobalMarkingVisitor visitor) {
-  traceImpl(visitor);
-}
-
-template <typename VisitorDispatcher>
-inline void ExternDerived::traceImpl(VisitorDispatcher visitor) {
   visitor->trace(x_derived_);
   ExternBase::trace(visitor);
 }