AU: Don't allow deltas if the rootfs track is different than the request track.

omaha_request_params.h

 // Copyright (c) 2010 The Chromium OS 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_OMAHA_REQUEST_PARAMS_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_OMAHA_REQUEST_PARAMS_H__
 
 #include <string>
 
 #include <base/basictypes.h>
@@ skipping 88 matching lines @@
 
   // Returns true if this is an official build, false otherwise.
   bool IsOfficialBuild() const;
 
   // Returns true if |track| is a valid track, false otherwise. This method
   // restricts the track value only if the image is official (see
   // IsOfficialBuild).
   bool IsValidTrack(const std::string& track) const;
 
   // Fetches the value for a given key from
-  // /mnt/stateful_partition/etc/lsb-release if possible. Failing that, it looks
-  // for the key in /etc/lsb-release. If |validator| is non-NULL, uses it to
-  // validate and ignore invalid valies.
+  // /mnt/stateful_partition/etc/lsb-release if possible and |stateful_override|
+  // is true. Failing that, it looks for the key in /etc/lsb-release. If
+  // |validator| is non-NULL, uses it to validate and ignore invalid valies.
   std::string GetLsbValue(const std::string& key,
                           const std::string& default_value,
-                          ValueValidator validator) const;
+                          ValueValidator validator,
+                          bool stateful_override) const;
 
   // Gets the machine type (e.g. "i686").
   std::string GetMachineType() const;
 
   // Returns the hardware qualification ID of the system, or empty
   // string if the HWID is unavailable.
   std::string GetHardwareClass() const;
 
   // When reading files, prepend root_ to the paths. Useful for testing.
   std::string root_;
 
   // Force build type for testing purposes.
   bool force_build_type_;
   bool forced_official_build_;
 
   DISALLOW_COPY_AND_ASSIGN(OmahaRequestDeviceParams);
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_OMAHA_REQUEST_PARAMS_H__