resources: Prevent including the same resource in multiple pack files.

ui/base/resource/resource_bundle.cc

 // Copyright (c) 2012 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 "ui/base/resource/resource_bundle.h"
 
 #include <limits>
 #include <vector>
 
 #include "base/big_endian.h"
@@ skipping 644 matching lines @@
       new DataPack(scale_factor));
   if (data_pack->LoadFromPath(pack_path)) {
     AddDataPack(data_pack.release());
   } else if (!optional) {
     LOG(ERROR) << "Failed to load " << pack_path.value()
                << "\nSome features may not be available.";
   }
 }
 
 void ResourceBundle::AddDataPack(DataPack* data_pack) {
+#if DCHECK_IS_ON()
+  data_pack->CheckForDuplicateResources(data_packs_);
+#endif
   data_packs_.push_back(data_pack);
 
   if (GetScaleForScaleFactor(data_pack->GetScaleFactor()) >
       GetScaleForScaleFactor(max_scale_factor_))
     max_scale_factor_ = data_pack->GetScaleFactor();
 }
 
 void ResourceBundle::InitDefaultFontList() {
 #if defined(OS_CHROMEOS)
   std::string font_family = base::UTF16ToUTF8(
@@ skipping 179 matching lines @@
 // static
 bool ResourceBundle::DecodePNG(const unsigned char* buf,
                                size_t size,
                                SkBitmap* bitmap,
                                bool* fell_back_to_1x) {
   *fell_back_to_1x = PNGContainsFallbackMarker(buf, size);
   return gfx::PNGCodec::Decode(buf, size, bitmap);
 }
 
 }  // namespace ui