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

tools/clang/blink_gc_plugin/RecordInfo.h

Index: tools/clang/blink_gc_plugin/RecordInfo.h
diff --git a/tools/clang/blink_gc_plugin/RecordInfo.h b/tools/clang/blink_gc_plugin/RecordInfo.h
index 1a25d8342b8a22b5c605079e4a1637be09ecaf5a..b294ffe03b61a1a7ee838c37a0458a2988bb53a8 100644
--- a/tools/clang/blink_gc_plugin/RecordInfo.h
+++ b/tools/clang/blink_gc_plugin/RecordInfo.h
@@ -69,8 +69,15 @@ class FieldPoint : public GraphPoint {
 // 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();