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

tools/clang/blink_gc_plugin/CheckTraceVisitor.cpp

 // Copyright 2015 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 "CheckTraceVisitor.h"
 
 #include <vector>
 
 #include "Config.h"
 
@@ skipping 342 matching lines @@
       }
     }
   }
   return true;
 }
 
 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) {
   if (Config::IsTemplateInstantiation(info_->record())) {
     // Pointer equality on fields does not work for template instantiations.
     // The trace method refers to fields of the template definition which
     // are different from the instantiated fields that need to be traced.
     const std::string& name = field->getNameAsString();
     for (RecordInfo::Fields::iterator it = info_->GetFields().begin();
          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));
   }
 }
 
 void CheckTraceVisitor::MarkAllWeakMembersTraced() {
   // If we find a call to registerWeakMembers which is unresolved we
   // unsoundly consider all weak members as traced.
   // TODO: Find out how to validate weak member tracing for unresolved call.
   for (auto& field : info_->GetFields()) {
     if (field.second.edge()->IsWeakMember())
       field.second.MarkTraced();
   }
 }