Don't send machine and user ID to Omaha anymore. Send a/r pings instead.

This avoids sending a unique ID in order to track active user counts.
Note that this CL doesn't remove the machine/user/Omaha ID/file from
the params object -- it just makes them unused/obsolete. Removal will
be done in a subsequent CL in an effort to make this CL smaller.

BUG=1439
TEST=unit tests, x86-generic, arm-generic, gmerged and inspected logs

Review URL: http://codereview.chromium.org/2856070
diff --git a/prefs_mock.h b/prefs_mock.h
new file mode 100644
index 0000000..cf030f0
--- /dev/null
+++ b/prefs_mock.h
@@ -0,0 +1,24 @@
+// 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_PREFS_MOCK_H__
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_PREFS_MOCK_H__
+
+#include "gmock/gmock.h"
+#include "update_engine/prefs_interface.h"
+
+namespace chromeos_update_engine {
+
+class PrefsMock : public PrefsInterface {
+ public:
+  MOCK_METHOD2(GetString, bool(const std::string& key, std::string* value));
+  MOCK_METHOD2(SetString, bool(const std::string& key,
+                               const std::string& value));
+  MOCK_METHOD2(GetInt64, bool(const std::string& key, int64_t* value));
+  MOCK_METHOD2(SetInt64, bool(const std::string& key, const int64_t value));
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_PREFS_MOCK_H__