[headless] Embed pak file into binary.

ui/base/resource/data_pack.h

Index: ui/base/resource/data_pack.h
diff --git a/ui/base/resource/data_pack.h b/ui/base/resource/data_pack.h
index 46578186f23161a22b61e0924ad6a84d82d95c1b..7ceba7ebbfb64b15f596f5d9a9e14c17eb4b52a8 100644
--- a/ui/base/resource/data_pack.h
+++ b/ui/base/resource/data_pack.h
@@ -50,6 +50,9 @@ class UI_DATA_PACK_EXPORT DataPack : public ResourceHandle {
   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);

[alex clarke (OOO till 29th), 2016/05/12 17:31:04]

bikeshed: Should this be InitializeFromBuffer?  Sami WDYT?

[altimin, 2016/05/12 18:07:53]

I don't think so — we already have LoadFromPath, LoadFromFile and
LoadFromFileRegion. For the sake of consistency I'd like it to be
LoadFromBuffer.

+
   // 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
@@ -75,11 +78,16 @@ class UI_DATA_PACK_EXPORT DataPack : public ResourceHandle {
 #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();
 
+  void Clear();
+
   // The memory-mapped data.

[alex clarke (OOO till 29th), 2016/05/12 17:31:04]

// The memory-mapped data.  Might be null if initialized from a memory buffer.

[altimin, 2016/05/12 18:07:53]

Acknowledged.

   std::unique_ptr<base::MemoryMappedFile> mmap_;

[alex clarke (OOO till 29th), 2016/05/12 17:31:04]

Not sure if this is overkill, but I would be tempted to add an inner class that
abstracts this, something like:

class DataSource {
  virtual size_t length() const = 0;
  virtual const uint8_t* data() const = 0;
};

Then have:

class MemoryMappedDataSource : public DataSource {
  size_t length() const override { return mmap_->length(); }
  const uint8_t* data() const override { return mmap_->data(); }

 private:
  std::unique_ptr<base::MemoryMappedFile> mmap_;
};

And the corresponding one for your in memory buffers.

This would amount to the same thing as your code, but I suspect it would be
easier to maintain, particularly if some third way of loading a file comes
along.

[altimin, 2016/05/12 18:07:53]

I thought about this and decided that's an overkill. But since you're thinking
about this too, we probably should do it.

+  size_t length_;
+  const uint8_t* data_;
 
   // Number of resources in the data.
   size_t resource_count_;