Merge to XFA: Sanitize CJBig2_SymbolDict's memory usage.

- Use std::vector<JBig2ArithCtx> instead of storing pointers to arrays.
- Make CJBig2_SymbolDict's members private with accessors.
- Use std::vector<JBig2ArithCtx> in related places.
- Steal Chromium's vector_as_array() and use it as an adaptor as needed.

BUG=514891
TBR=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1388203003 .

(cherry picked from commit 3acb1ef909a22368507ed13817c4988c818e3aee)

Review URL: https://codereview.chromium.org/1401533004 .

1 files changed, 27 insertions, 0 deletions

diff --git a/third_party/base/stl_util.h b/third_party/base/stl_util.h
new file mode 100644
index 0000000000..fcbe5882a2
--- /dev/null
+++ b/third_party/base/stl_util.h
@@ -0,0 +1,27 @@
+// 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.
+
+#ifndef PDFIUM_THIRD_PARTY_BASE_STL_UTIL_H_
+#define PDFIUM_THIRD_PARTY_BASE_STL_UTIL_H_
+
+#include <vector>
+
+namespace pdfium {
+
+// To treat a possibly-empty vector as an array, use these functions.
+// If you know the array will never be empty, you can use &*v.begin()
+// directly, but that is undefined behaviour if |v| is empty.
+template <typename T>
+inline T* vector_as_array(std::vector<T>* v) {
+  return v->empty() ? nullptr : &*v->begin();
+}
+
+template <typename T>
+inline const T* vector_as_array(const std::vector<T>* v) {
+  return v->empty() ? nullptr : &*v->begin();
+}
+
+}  // namespace pdfium
+
+#endif  // PDFIUM_THIRD_PARTY_BASE_STL_UTIL_H_