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

tools/clang/blink_gc_plugin/CheckTraceVisitor.cpp

Index: tools/clang/blink_gc_plugin/CheckTraceVisitor.cpp
diff --git a/tools/clang/blink_gc_plugin/CheckTraceVisitor.cpp b/tools/clang/blink_gc_plugin/CheckTraceVisitor.cpp
index c996ca7dd1480a76c65ddf12f3fd8d2215aa7009..d5055c8860c2ed9b34a38c6f5872a01b3dd9e70c 100644
--- a/tools/clang/blink_gc_plugin/CheckTraceVisitor.cpp
+++ b/tools/clang/blink_gc_plugin/CheckTraceVisitor.cpp
@@ -360,11 +360,11 @@ bool CheckTraceVisitor::IsWeakCallback() const {
   return !trace_;
 }
 
-void CheckTraceVisitor::MarkTraced(RecordInfo::Fields::iterator it) {
+void CheckTraceVisitor::MarkTraced(RecordInfo::Field& field) {
   // In a weak callback we can't mark strong fields as traced.
-  if (IsWeakCallback() && !it->second.edge()->IsWeakMember())
+  if (IsWeakCallback() && !field.second.edge()->IsWeakMember())
     return;
-  it->second.MarkTraced();
+  field.second.MarkTraced();
 }
 
 void CheckTraceVisitor::FoundField(FieldDecl* field) {
@@ -377,14 +377,13 @@ void CheckTraceVisitor::FoundField(FieldDecl* field) {
          it != info_->GetFields().end();
          ++it) {
       if (it->first->getNameAsString() == name) {
-        MarkTraced(it);
+        MarkTraced(*it);
         break;
       }
     }
   } else {
-    RecordInfo::Fields::iterator it = info_->GetFields().find(field);
-    if (it != info_->GetFields().end())
-      MarkTraced(it);
+    if (info_->HasField(field))
+      MarkTraced(info_->GetField(field));
   }
 }