blink_gc_plugin: retire overloaded traceImpl detection and handling.

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

Index: tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded_error.cpp
diff --git a/tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded_error.cpp b/tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded_error.cpp
index 07cab63e7af79eae5b31d162d5072420fff63bdb..478ad7d66898bf3b5d282a2159ea4e2d77fa07f4 100644
--- a/tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded_error.cpp
+++ b/tools/clang/blink_gc_plugin/tests/legacy_naming/traceimpl_overloaded_error.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) {
   // Missing 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) {
   // Missing visitor->trace(x_derived_) and ExternBase::trace(visitor).
 }