[headless] Embed pak file into binary.

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 15 matching lines @@
 namespace base {
 class FilePath;
 class RefCountedStaticMemory;
 }
 
 namespace ui {
 enum ScaleFactor : int;
 
 class UI_DATA_PACK_EXPORT DataPack : public ResourceHandle {
  public:
+  class DataSource;
+
   explicit DataPack(ui::ScaleFactor scale_factor);
   ~DataPack() override;
 
   void set_has_only_material_design_assets(bool has_only_material_assets) {
     has_only_material_design_assets_ = has_only_material_assets;
   }
 
   // Load a pack file from |path|, returning false on error.
   bool LoadFromPath(const base::FilePath& path);
 
   // Loads a pack file from |file|, returning false on error.
   bool LoadFromFile(base::File file);
 
   // Loads a pack file from |region| of |file|, returning false on error.
   bool LoadFromFileRegion(base::File file,
                           const base::MemoryMappedFile::Region& region);
 
+  // Loads a pack file from |buffer|, returning false on error.
+  bool LoadFromBuffer(base::StringPiece buffer);

[sky, 2016/05/19 20:25:54]

LoadFromStringPiece?
Also, I think it's worth mentioning life time. Specifically that this code does
*not* make a copy of the data.

[altimin, 2016/05/19 23:04:47]

I believe that LoadFromBuffer describes it more precisely, usage of StringPiece
for storing buffer is just an implementation detail.

Comment added.

+
   // Writes a pack file containing |resources| to |path|. If there are any
   // text resources to be written, their encoding must already agree to the
   // |textEncodingType| specified. If no text resources are present, please
   // indicate BINARY.
   static bool WritePack(const base::FilePath& path,
                         const std::map<uint16_t, base::StringPiece>& resources,
                         TextEncodingType textEncodingType);
 
   // ResourceHandle implementation:
   bool HasResource(uint16_t resource_id) const override;
   bool GetStringPiece(uint16_t resource_id,
                       base::StringPiece* data) const override;
   base::RefCountedStaticMemory* GetStaticMemory(
       uint16_t resource_id) const override;
   TextEncodingType GetTextEncodingType() const override;
   ui::ScaleFactor GetScaleFactor() const override;
   bool HasOnlyMaterialDesignAssets() 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.
+  // Does the actual loading of a pack file.
+  // Called by Load and LoadFromFile and LoadFromBuffer.
   bool LoadImpl();
 
-  // The memory-mapped data.
-  std::unique_ptr<base::MemoryMappedFile> mmap_;
+  std::unique_ptr<DataSource> data_source_;
 
   // 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_;
 
   // Set to true if the only resources contained within this DataPack are
   // material design image assets.
   bool has_only_material_design_assets_;
 
   DISALLOW_COPY_AND_ASSIGN(DataPack);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_RESOURCE_DATA_PACK_H_