Add support for loading pak files from arbitrary file regions.

ui/base/resource/resource_bundle.cc

Index: ui/base/resource/resource_bundle.cc
diff --git a/ui/base/resource/resource_bundle.cc b/ui/base/resource/resource_bundle.cc
index b2be5e460c2a7eff2d0acf2f90bb3e6cef5d4555..a9786aac2d2676f998781206dc4ac6cf041b6c71 100644
--- a/ui/base/resource/resource_bundle.cc
+++ b/ui/base/resource/resource_bundle.cc
@@ -234,9 +234,17 @@ void ResourceBundle::AddOptionalDataPackFromPath(const base::FilePath& path,
 
 void ResourceBundle::AddDataPackFromFile(base::File file,
                                          ScaleFactor scale_factor) {
+  AddDataPackFromFileRegion(
+      file.Pass(), base::MemoryMappedFile::Region::kWholeFile, scale_factor);
+}
+
+void ResourceBundle::AddDataPackFromFileRegion(
+    base::File file,
+    const base::MemoryMappedFile::Region& region,
+    ScaleFactor scale_factor) {
   scoped_ptr<DataPack> data_pack(
       new DataPack(scale_factor));
-  if (data_pack->LoadFromFile(file.Pass())) {
+  if (data_pack->LoadFromFileRegion(file.Pass(), region)) {
     AddDataPack(data_pack.release());
   } else {
     LOG(ERROR) << "Failed to load data pack from file."