GC plugin: RefPtr<T> is legal if T is RefCountedGC-derived.

tools/clang/blink_gc_plugin/RecordInfo.cpp

Index: tools/clang/blink_gc_plugin/RecordInfo.cpp
diff --git a/tools/clang/blink_gc_plugin/RecordInfo.cpp b/tools/clang/blink_gc_plugin/RecordInfo.cpp
index 516a40a04daec50f420e1262ef2cff2d4a349202..cf7fb8c578e80ed3e4b6c1f78e83260e1848dda2 100644
--- a/tools/clang/blink_gc_plugin/RecordInfo.cpp
+++ b/tools/clang/blink_gc_plugin/RecordInfo.cpp
@@ -186,6 +186,16 @@ bool RecordInfo::IsEagerlyFinalized() {
   return is_eagerly_finalized_;
 }
 
+bool RecordInfo::IsGCRefCounted() {
+  if (!IsGCDerived())
+    return false;
+  for (const auto& gc_base : gc_base_names_) {
+    if (Config::IsGCRefCountedBase(gc_base))
+      return true;
+  }
+  return false;
+}
+
 bool RecordInfo::HasDefinition() {
   return record_->hasDefinition();
 }