Blink GC plugin: require a trace method if a class derives multiple bases that need tracing.

tools/clang/blink_gc_plugin/RecordInfo.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 provides a wrapper for CXXRecordDecl that accumulates GC related
 // information about a class. Accumulated information is memoized and the info
 // objects are stored in a RecordCache.
 
 #ifndef TOOLS_BLINK_GC_PLUGIN_RECORD_INFO_H_
 #define TOOLS_BLINK_GC_PLUGIN_RECORD_INFO_H_
@@ skipping 20 matching lines @@
   bool traced_;
 };
 
 class BasePoint : public GraphPoint {
  public:
   BasePoint(const clang::CXXBaseSpecifier& spec,
             RecordInfo* info,
             const TracingStatus& status)
       : spec_(spec), info_(info), status_(status) {}
   const TracingStatus NeedsTracing() { return status_; }
-  // Needed to change the status of bases with a pure-virtual trace.
-  void MarkUnneeded() { status_ = TracingStatus::Unneeded(); }
   const clang::CXXBaseSpecifier& spec() { return spec_; }
   RecordInfo* info() { return info_; }
 
  private:
   const clang::CXXBaseSpecifier& spec_;
   RecordInfo* info_;
   TracingStatus status_;
 };
 
 class FieldPoint : public GraphPoint {
@@ skipping 114 matching lines @@
       }
     }
   }
 
  private:
   typedef std::map<clang::CXXRecordDecl*, RecordInfo> Cache;
   Cache cache_;
 };
 
 #endif  // TOOLS_BLINK_GC_PLUGIN_RECORD_INFO_H_