Add CPDF_{Array,Dictionary}Locker to catch illegal iteration patterns.

Move begin/end methods onto locker object which tracks whether
iterators are in existence.

Change-Id: Ia869f313fce48d10a0d0180d0cc083eed6ea1584
Reviewed-on: https://pdfium-review.googlesource.com/c/44070
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

1 files changed, 2 insertions, 4 deletions

diff --git a/core/fpdfapi/parser/cpdf_cross_ref_table.cpp b/core/fpdfapi/parser/cpdf_cross_ref_table.cpp
index 4f7c482c9f..31e9fd3f62 100644
--- a/core/fpdfapi/parser/cpdf_cross_ref_table.cpp
+++ b/core/fpdfapi/parser/cpdf_cross_ref_table.cpp
@@ -5,6 +5,7 @@
 #include "core/fpdfapi/parser/cpdf_cross_ref_table.h"
 
 #include <utility>
+#include <vector>
 
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fpdfapi/parser/cpdf_parser.h"
@@ -153,9 +154,6 @@ void CPDF_CrossRefTable::UpdateTrailer(
   new_trailer->SetFor("XRefStm", trailer_->RemoveFor("XRefStm"));
   new_trailer->SetFor("Prev", trailer_->RemoveFor("Prev"));
 
-  for (auto it = new_trailer->begin(); it != new_trailer->end();) {
-    const ByteString key = it->first;
-    ++it;
+  for (const auto& key : new_trailer->GetKeys())
     trailer_->SetFor(key, new_trailer->RemoveFor(key));
-  }
 }