Emit notes from ReportClassRequiresTraceMethod in deterministic order

tools/clang/blink_gc_plugin/BlinkGCPluginConsumer.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 "BlinkGCPluginConsumer.h"
 
 #include <algorithm>
 #include <set>
 
 #include "CheckDispatchVisitor.h"
@@ skipping 955 matching lines @@
   ReportDiagnostic(info->record()->getInnerLocStart(),
                    diag_class_must_left_mostly_derive_gc_)
       << info->record();
 }
 
 void BlinkGCPluginConsumer::ReportClassRequiresTraceMethod(RecordInfo* info) {
   ReportDiagnostic(info->record()->getInnerLocStart(),
                    diag_class_requires_trace_method_)
       << info->record();
 
-  for (RecordInfo::Bases::iterator it = info->GetBases().begin();
-       it != info->GetBases().end();
-       ++it) {
-    if (it->second.NeedsTracing().IsNeeded())
-      NoteBaseRequiresTracing(&it->second);
+  // Use an intermediate map to sort the notes by source location.
+  std::map<clang::SourceLocation, BasePoint*> BaseNotes;
+  for (auto& pair : info->GetBases()) {
+    if (pair.second.NeedsTracing().IsNeeded())
+      BaseNotes.insert(std::make_pair(pair.first->getLocStart(), &pair.second));
   }
+  for (auto& pair : BaseNotes)
+    NoteBaseRequiresTracing(pair.second);
 
-  for (RecordInfo::Fields::iterator it = info->GetFields().begin();
-       it != info->GetFields().end();
-       ++it) {
-    if (!it->second.IsProperlyTraced())
-      NoteFieldRequiresTracing(info, it->first);
+  // Use an intermediate map to sort the notes by source location.
+  std::map<clang::SourceLocation, clang::FieldDecl*> FieldNotes;
+  for (auto& pair : info->GetFields()) {
+    if (!pair.second.IsProperlyTraced())
+      FieldNotes.insert(std::make_pair(pair.first->getLocStart(), pair.first));
   }
+  for (auto& pair : FieldNotes)
+    NoteFieldRequiresTracing(info, pair.second);
 }
 
 void BlinkGCPluginConsumer::ReportBaseRequiresTracing(
     RecordInfo* derived,
     CXXMethodDecl* trace,
     CXXRecordDecl* base) {
   ReportDiagnostic(trace->getLocStart(), diag_base_requires_tracing_)
       << base << derived->record();
 }
 
@@ skipping 246 matching lines @@
 void BlinkGCPluginConsumer::NoteField(FieldDecl* field, unsigned note) {
   ReportDiagnostic(field->getLocStart(), note) << field;
 }
 
 void BlinkGCPluginConsumer::NoteOverriddenNonVirtualTrace(
     CXXMethodDecl* overridden) {
   ReportDiagnostic(overridden->getLocStart(),
                    diag_overridden_non_virtual_trace_note_)
       << overridden;
 }