blink_gc_plugin: retire overloaded traceImpl detection and handling.

tools/clang/blink_gc_plugin/tests/traceimpl.cpp

Index: tools/clang/blink_gc_plugin/tests/traceimpl.cpp
diff --git a/tools/clang/blink_gc_plugin/tests/traceimpl.cpp b/tools/clang/blink_gc_plugin/tests/traceimpl.cpp
index fe28a0b4b65218844074e9677ffbbde7877fb8b5..84e71208ded99af8c9aae21968376e957ac4d172 100644
--- a/tools/clang/blink_gc_plugin/tests/traceimpl.cpp
+++ b/tools/clang/blink_gc_plugin/tests/traceimpl.cpp
@@ -7,20 +7,10 @@
 namespace blink {
 
 void TraceImplExtern::Trace(Visitor* visitor) {
-  TraceImpl(visitor);
-}
-
-template <typename VisitorDispatcher>
-inline void TraceImplExtern::TraceImpl(VisitorDispatcher visitor) {
   visitor->Trace(x_);
 }
 
 void TraceImplBaseExtern::Trace(Visitor* visitor) {
-  TraceImpl(visitor);
-}
-
-template <typename VisitorDispatcher>
-inline void TraceImplBaseExtern::TraceImpl(VisitorDispatcher visitor) {
   visitor->Trace(x_);
   Base::Trace(visitor);
 }