Revert of GC plugin: improve error reporting when tracing illegal fields.

tools/clang/blink_gc_plugin/Edge.cpp

Index: tools/clang/blink_gc_plugin/Edge.cpp
diff --git a/tools/clang/blink_gc_plugin/Edge.cpp b/tools/clang/blink_gc_plugin/Edge.cpp
index 77c6cfec4ba9013dd0988075a4093d851471d571..c56a576414896e0bf9998fe1358341484c278d31 100644
--- a/tools/clang/blink_gc_plugin/Edge.cpp
+++ b/tools/clang/blink_gc_plugin/Edge.cpp
@@ -17,11 +17,9 @@
 void RecursiveEdgeVisitor::AtRawPtr(RawPtr*) {}
 void RecursiveEdgeVisitor::AtRefPtr(RefPtr*) {}
 void RecursiveEdgeVisitor::AtOwnPtr(OwnPtr*) {}
-void RecursiveEdgeVisitor::AtUniquePtr(UniquePtr*) {}
 void RecursiveEdgeVisitor::AtMember(Member*) {}
 void RecursiveEdgeVisitor::AtWeakMember(WeakMember*) {}
 void RecursiveEdgeVisitor::AtPersistent(Persistent*) {}
-void RecursiveEdgeVisitor::AtCrossThreadPersistent(CrossThreadPersistent*) {}
 void RecursiveEdgeVisitor::AtCollection(Collection*) {}
 
 void RecursiveEdgeVisitor::VisitValue(Value* e) {
@@ -48,13 +46,6 @@
   Leave();
 }
 
-void RecursiveEdgeVisitor::VisitUniquePtr(UniquePtr* e) {
-  AtUniquePtr(e);
-  Enter(e);
-  e->ptr()->Accept(this);
-  Leave();
-}
-
 void RecursiveEdgeVisitor::VisitMember(Member* e) {
   AtMember(e);
   Enter(e);
@@ -76,14 +67,6 @@
   Leave();
 }
 
-void RecursiveEdgeVisitor::VisitCrossThreadPersistent(
-    CrossThreadPersistent* e) {
-  AtCrossThreadPersistent(e);
-  Enter(e);
-  e->ptr()->Accept(this);
-  Leave();
-}
-
 void RecursiveEdgeVisitor::VisitCollection(Collection* e) {
   AtCollection(e);
   Enter(e);