Reland of Add deduplication logic to .pak 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_
@@ skipping 57 matching lines @@
   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 std::vector<std::unique_ptr<ResourceHandle>>& packs);
 #endif
 
  private:
+  struct Entry;
+  struct Alias;
   class DataSource;
   class BufferDataSource;
   class MemoryMappedDataSource;
 
   // Does the actual loading of a pack file.
   // Called by Load and LoadFromFile and LoadFromBuffer.
   bool LoadImpl(std::unique_ptr<DataSource> data_source);
+  const Entry* LookupEntryById(uint16_t resource_id) const;
 
   std::unique_ptr<DataSource> data_source_;
 
-  // Number of resources in the data.
+  const Entry* resource_table_;
   size_t resource_count_;
+  const Alias* alias_table_;
+  size_t alias_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_