AU: Start checkpointing update progress.

Checkpoint the manifest metadata size and the update
check response hash in the preference store. Also checkpoint
the next operation and data offset.
Add methods for getting/setting hash context.

BUG=7390,7394
TEST=unit tests

Change-Id: I25291bf598ac9b0f1033e11cfe59df45b1f6eeab

Review URL: http://codereview.chromium.org/3521016
diff --git a/omaha_response_handler_action_unittest.cc b/omaha_response_handler_action_unittest.cc
index 90cbed9..10be7d6 100644
--- a/omaha_response_handler_action_unittest.cc
+++ b/omaha_response_handler_action_unittest.cc
@@ -1,14 +1,18 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// 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.
 
 #include <string>
+
 #include <gtest/gtest.h>
+
 #include "update_engine/omaha_response_handler_action.h"
+#include "update_engine/prefs_mock.h"
 #include "update_engine/test_utils.h"
 #include "update_engine/utils.h"
 
 using std::string;
+using testing::Return;
 
 namespace chromeos_update_engine {
 
@@ -60,7 +64,12 @@
 
   ObjectFeederAction<OmahaResponse> feeder_action;
   feeder_action.set_obj(in);
-  OmahaResponseHandlerAction response_handler_action;
+  PrefsMock prefs;
+  if (in.update_exists) {
+    EXPECT_CALL(prefs, SetString(kPrefsUpdateCheckResponseHash, in.hash))
+        .WillOnce(Return(true));
+  }
+  OmahaResponseHandlerAction response_handler_action(&prefs);
   response_handler_action.set_boot_device(boot_dev);
   BondActions(&feeder_action, &response_handler_action);
   ObjectCollectorAction<InstallPlan> collector_action;