AU: Try delta updates first, then full updates

src/platform/update_engine/SConstruct

 # Copyright (c) 2009 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.
 
 # Protobuffer compilation
 """ Inputs:
         target: list of targets to compile to
         source: list of sources to compile
         env: the scons environment in which we are compiling
     Outputs:
@@ skipping 105 matching lines @@
                             omaha_response_handler_action_unittest.cc
                             postinstall_runner_action_unittest.cc
                             set_bootable_flag_action_unittest.cc
                             subprocess_unittest.cc
                             test_utils.cc
                             update_check_action_unittest.cc
                             utils_unittest.cc""")
 unittest_main = ['testrunner.cc']
 
 delta_generator_sources = Split("""delta_diff_generator.cc""")
+delta_generator_main = ['generate_delta_main.cc']
+
+test_installer_main = ['test_installer_main.cc']
 
 env.Program('update_engine', sources + main)
 unittest_cmd = env.Program('update_engine_unittests',
                            sources + delta_generator_sources +
                            unittest_sources + unittest_main)
 
+test_installer_cmd = env.Program('test_installer',
+                                 sources + delta_generator_sources +
+                                 unittest_sources + test_installer_main)
+
 Clean(unittest_cmd, Glob('*.gcda') + Glob('*.gcno') + Glob('*.gcov') +
                     Split('html app.info'))
 
 delta_generator_cmd = env.Program('delta_generator',
-                                  sources + delta_generator_sources + main)
+                                  sources + delta_generator_sources +
+                                  delta_generator_main)
 
 http_server_cmd = env.Program('test_http_server', 'test_http_server.cc')