AU: Update Downloader to support our image formats.

src/platform/update_engine/utils.h

 // Copyright (c) 2009 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_UTILS_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_UTILS_H__
 
 #include <errno.h>
 #include <algorithm>
 #include <set>
@@ skipping 117 matching lines @@
                                                          vect.end(),
                                                          value);
   if (it == vect.end()) {
     return false;
   } else {
     *out_index = it - vect.begin();
     return true;
   }
 }
 
-// Returns the currently booted device. "/dev/sda1", for example.
+// Returns the currently booted device. "/dev/sda3", for example.
 // This will not interpret LABEL= or UUID=. You'll need to use findfs
 // or something with equivalent funcionality to interpret those.
 const std::string BootDevice();
 
+// Returns the currently booted kernel device, "dev/sda2", for example.
+// Client must pass in the boot device. The suggested calling convention
+// is: BootKernelDevice(BootDevice()).
+// This function works by doing string modification on boot_device.
+// Returns empty string on failure.
+const std::string BootKernelDevice(const std::string& boot_device);
+
+
 }  // namespace utils
 
 // Class to unmount FS when object goes out of scope
 class ScopedFilesystemUnmounter {
  public:
   explicit ScopedFilesystemUnmounter(const std::string& mountpoint)
       : mountpoint_(mountpoint) {}
   ~ScopedFilesystemUnmounter() {
     utils::UnmountFilesystem(mountpoint_);
   }
@@ skipping 115 matching lines @@
     bool _success = (_x);                                                      \
     if (!_success) {                                                           \
       LOG(ERROR) << #_x " failed.";                                            \
       return;                                                                  \
     }                                                                          \
   } while (0)
 
 
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_UTILS_H__