Revert of mojo filesystem: Simplify full file reading/writing.

components/filesystem/file_impl.h

 // Copyright 2015 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.
 
 #ifndef COMPONENTS_FILESYSTEM_FILE_IMPL_H_
 #define COMPONENTS_FILESYSTEM_FILE_IMPL_H_
 
 #include <stdint.h>
 
 #include "base/files/file.h"
@@ skipping 16 matching lines @@
            uint32_t flags);
   FileImpl(mojo::InterfaceRequest<File> request, base::File file);
   ~FileImpl() override;
 
   // |File| implementation:
   void Close(const CloseCallback& callback) override;
   void Read(uint32_t num_bytes_to_read,
             int64_t offset,
             Whence whence,
             const ReadCallback& callback) override;
+  void ReadEntireFile(const ReadEntireFileCallback& callback) override;
   void Write(mojo::Array<uint8_t> bytes_to_write,
              int64_t offset,
              Whence whence,
              const WriteCallback& callback) override;
   void Tell(const TellCallback& callback) override;
   void Seek(int64_t offset,
             Whence whence,
             const SeekCallback& callback) override;
   void Stat(const StatCallback& callback) override;
   void Truncate(int64_t size, const TruncateCallback& callback) override;
   void Touch(TimespecOrNowPtr atime,
              TimespecOrNowPtr mtime,
              const TouchCallback& callback) override;
   void Dup(mojo::InterfaceRequest<File> file,
            const DupCallback& callback) override;
   void Flush(const FlushCallback& callback) override;
   void AsHandle(const AsHandleCallback& callback) override;
 
  private:
   mojo::StrongBinding<File> binding_;
   base::File file_;
 
   DISALLOW_COPY_AND_ASSIGN(FileImpl);
 };
 
 }  // namespace filesystem
 
 #endif  // COMPONENTS_FILESYSTEM_FILE_IMPL_H_