Fix an integer overflow in CStretchEngine constructor

core/fxge/dib/fx_dib_engine_unittest.cpp

+// Copyright 2016 PDFium 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 <memory>
+
+#include "core/fpdfapi/fpdf_parser/include/cpdf_dictionary.h"
+#include "core/fpdfapi/fpdf_parser/include/cpdf_number.h"
+#include "core/fpdfapi/fpdf_parser/include/cpdf_stream.h"
+#include "core/fpdfapi/fpdf_render/render_int.h"
+#include "core/fxcrt/include/fx_memory.h"
+#include "core/fxge/dib/dib_int.h"
+#include "core/fxge/include/fx_dib.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+TEST(CStretchEngine, OverflowInCtor) {
+  FX_RECT clip_rect;
+  std::unique_ptr<CPDF_Dictionary, ReleaseDeleter<CPDF_Dictionary>> dict_obj(
+      new CPDF_Dictionary);
+  dict_obj->SetAt("Width", new CPDF_Number(71000));
+  dict_obj->SetAt("Height", new CPDF_Number(12500));
+  std::unique_ptr<CPDF_Stream, ReleaseDeleter<CPDF_Stream>> stream(
+      new CPDF_Stream(nullptr, 0, dict_obj.release()));
+  CPDF_DIBSource dib_source;
+  dib_source.Load(nullptr, stream.get(), nullptr, nullptr, nullptr, nullptr,
+                  false, 0, false);
+  CStretchEngine engine(nullptr, FXDIB_8bppRgb, 500, 500, clip_rect,
+                        &dib_source, 0);
+  EXPECT_EQ(FXDIB_INTERPOL, engine.m_Flags);
+}