blink_gc_plugin: retire overloaded traceImpl detection and handling.

tools/clang/blink_gc_plugin/tests/traceimpl_omitted_trace.h

Index: tools/clang/blink_gc_plugin/tests/traceimpl_omitted_trace.h
diff --git a/tools/clang/blink_gc_plugin/tests/traceimpl_omitted_trace.h b/tools/clang/blink_gc_plugin/tests/traceimpl_omitted_trace.h
index 7a171be8065fa259b3d940b0fe2fa9de48bb2f73..6b359659ecd1813a30ffbdb0538ea8154b4b81dd 100644
--- a/tools/clang/blink_gc_plugin/tests/traceimpl_omitted_trace.h
+++ b/tools/clang/blink_gc_plugin/tests/traceimpl_omitted_trace.h
@@ -11,14 +11,7 @@ namespace blink {
 
 class A : public GarbageCollected<A> {
  public:
-  virtual void Trace(Visitor* visitor) { TraceImpl(visitor); }
-  virtual void Trace(InlinedGlobalMarkingVisitor visitor) {
-    TraceImpl(visitor);
-  }
-
- private:
-  template <typename VisitorDispatcher>
-  void TraceImpl(VisitorDispatcher visitor) {}
+  virtual void Trace(Visitor* visitor) {}
 };
 
 class B : public A {
@@ -27,14 +20,7 @@ class B : public A {
 
 class C : public B {
  public:
-  void Trace(Visitor* visitor) override { TraceImpl(visitor); }
-  void Trace(InlinedGlobalMarkingVisitor visitor) override {
-    TraceImpl(visitor);
-  }
-
- private:
-  template <typename VisitorDispatcher>
-  void TraceImpl(VisitorDispatcher visitor) {
+  void Trace(Visitor* visitor) override {
     // B::Trace() is actually A::Trace(), and in certain cases we only get
     // limited information like "there is a function call that will be resolved
     // to A::Trace()". We still want to mark B as Traced.