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

ui/base/resource/data_pack.h

 // 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.
 
 // DataPack represents a read-only view onto an on-disk file that contains
 // (key, value) pairs of data.  It's used to store static resources like
 // translation strings and images.
 
 #ifndef UI_BASE_RESOURCE_DATA_PACK_H_
 #define UI_BASE_RESOURCE_DATA_PACK_H_
 
 #include <map>
 
 #include "base/basictypes.h"
 #include "base/files/file.h"
 #include "base/files/memory_mapped_file.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
 #include "base/strings/string_piece.h"
 #include "ui/base/resource/resource_handle.h"
 #include "ui/base/ui_base_export.h"
 
 namespace base {
 class FilePath;
 class RefCountedStaticMemory;
 }
 
 namespace ui {
@@ skipping 24 matching lines @@
 
   // ResourceHandle implementation:
   bool HasResource(uint16 resource_id) const override;
   bool GetStringPiece(uint16 resource_id,
                       base::StringPiece* data) const override;
   base::RefCountedStaticMemory* GetStaticMemory(
       uint16 resource_id) const override;
   TextEncodingType GetTextEncodingType() const override;
   ui::ScaleFactor GetScaleFactor() const override;
 
+#if DCHECK_IS_ON()
+  // Checks to see if any resource in this DataPack already exists in the list
+  // of resources.
+  void CheckForDuplicateResources(const ScopedVector<ResourceHandle>& packs);
+#endif
+
  private:
   // Does the actual loading of a pack file. Called by Load and LoadFromFile.
   bool LoadImpl();
 
   // The memory-mapped data.
   scoped_ptr<base::MemoryMappedFile> mmap_;
 
   // Number of resources in the data.
   size_t resource_count_;
 
   // Type of encoding for text resources.
   TextEncodingType text_encoding_type_;
 
   // The scale of the image in this resource pack relative to images in the 1x
   // resource pak.
   ui::ScaleFactor scale_factor_;
 
   DISALLOW_COPY_AND_ASSIGN(DataPack);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_RESOURCE_DATA_PACK_H_