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

tools/clang/blink_gc_plugin/RecordInfo.cpp

 // 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.
 
 #include "Config.h"
 #include "RecordInfo.h"
 
 using namespace clang;
 using std::string;
 
@@ skipping 168 matching lines @@
             is_eagerly_finalized_ = kTrue;
             break;
           }
         }
       }
     }
   }
   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();
 }
 
 RecordInfo* RecordCache::Lookup(CXXRecordDecl* record) {
   // Ignore classes annotated with the GC_PLUGIN_IGNORE macro.
   if (!record || Config::IsIgnoreAnnotated(record))
     return 0;
   Cache::iterator it = cache_.find(record);
   if (it != cache_.end())
@@ skipping 465 matching lines @@
         edge->members().push_back(member);
       }
       // TODO: Handle the case where we fail to create an edge (eg, if the
       // argument is a primitive type or just not fully known yet).
     }
     return edge;
   }
 
   return new Value(info);
 }