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

tools/clang/blink_gc_plugin/Config.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file defines the names used by GC infrastructure.
 
 // TODO: Restructure the name determination to use fully qualified names (ala,
 // blink::Foo) so that the plugin can be enabled for all of chromium. Doing so
 // would allow us to catch errors with structures outside of blink that might
 // have unsafe pointers to GC allocated blink structures.
@@ skipping 120 matching lines @@
   static bool IsGCMixinBase(const std::string& name) {
     return name == "GarbageCollectedMixin";
   }
 
   static bool IsGCFinalizedBase(const std::string& name) {
     return name == "GarbageCollectedFinalized" ||
            name == "RefCountedGarbageCollected" ||
            name == "ThreadSafeRefCountedGarbageCollected";
   }
 
+  static bool IsGCRefCountedBase(const std::string& name) {
+    return name == "RefCountedGarbageCollected" ||
+           name == "ThreadSafeRefCountedGarbageCollected";
+  }
+
   static bool IsGCBase(const std::string& name) {
     return name == "GarbageCollected" ||
            IsGCFinalizedBase(name) ||
            IsGCMixinBase(name);
   }
 
   // Returns true of the base classes that do not need a vtable entry for trace
   // because they cannot possibly initiate a GC during construction.
   static bool IsSafePolymorphicBase(const std::string& name) {
     return IsGCBase(name) || IsDummyBase(name) || IsRefCountedBase(name);
@@ skipping 112 matching lines @@
     if (suffix.size() > str.size())
       return false;
     return str.compare(str.size() - suffix.size(), suffix.size(), suffix) == 0;
   }
 
   // Test if a template specialization is an instantiation.
   static bool IsTemplateInstantiation(clang::CXXRecordDecl* record);
 };
 
 #endif  // TOOLS_BLINK_GC_PLUGIN_CONFIG_H_