blink_gc_plugin: Make RecordInfo::Get{Fields,Bases} return deterministic order

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 51 matching lines @@
   clang::FieldDecl* field_;
   Edge* edge_;
 
   friend class RecordCache;
   void deleteEdge() { delete edge_; }
 };
 
 // Wrapper class to lazily collect information about a C++ record.
 class RecordInfo {
  public:
-  typedef std::map<clang::CXXRecordDecl*, BasePoint> Bases;
-  typedef std::map<clang::FieldDecl*, FieldPoint> Fields;
+  typedef std::vector<std::pair<clang::CXXRecordDecl*, BasePoint>> Bases;
+
+  struct FieldDeclCmp {
+    bool operator()(clang::FieldDecl* a, clang::FieldDecl *b) const {
+      return a->getLocStart() < b->getLocStart();
+    }
+  };
+  typedef std::map<clang::FieldDecl*, FieldPoint, FieldDeclCmp> Fields;
+
   typedef std::vector<const clang::Type*> TemplateArgs;
 
   ~RecordInfo();
 
   clang::CXXRecordDecl* record() const { return record_; }
   const std::string& name() const { return name_; }
   Fields& GetFields();
   Bases& GetBases();
   clang::CXXMethodDecl* GetTraceMethod();
   clang::CXXMethodDecl* GetTraceDispatchMethod();
@@ skipping 97 matching lines @@
       }
     }
   }
 
  private:
   typedef std::map<clang::CXXRecordDecl*, RecordInfo> Cache;
   Cache cache_;
 };
 
 #endif  // TOOLS_BLINK_GC_PLUGIN_RECORD_INFO_H_