Add support for loading pak files from arbitrary file regions.

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 4d9d4bbdc2f9eea9012b20a0a25af8de09626a0d..2eeb1b2183e022d85a477037e317e2f84be7f67b 100644
--- a/ui/base/resource/data_pack.h
+++ b/ui/base/resource/data_pack.h
@@ -13,6 +13,7 @@
 
 #include "base/basictypes.h"
 #include "base/files/file.h"
+#include "base/files/memory_mapped_file.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string_piece.h"
 #include "ui/base/layout.h"
@@ -21,7 +22,6 @@
 
 namespace base {
 class FilePath;
-class MemoryMappedFile;
 class RefCountedStaticMemory;
 }
 
@@ -38,6 +38,10 @@ class UI_BASE_EXPORT DataPack : public ResourceHandle {
   // 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);
+
   // 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