AU: DBus support.

A few changes to support dbus in the Update Engine daemon:

- SConstruct: build marshaller for the dbus signal.

- Update Attempter: respond to dbus calls and broadcast status on dbus
  signal.

- Update Engine Client: flag to listen for status updates.

- Also, cleanup outdated code in Omaha Response Handler.

BUG=None
TEST=attached unittests/on device tests

Review URL: http://codereview.chromium.org/2037002
diff --git a/omaha_response_handler_action.h b/omaha_response_handler_action.h
index b56d343..e79e32b 100644
--- a/omaha_response_handler_action.h
+++ b/omaha_response_handler_action.h
@@ -43,6 +43,7 @@
   }
   
   bool GotNoUpdateResponse() const { return got_no_update_response_; }
+  const InstallPlan& install_plan() const { return install_plan_; }
 
   // Debugging/logging
   static std::string StaticType() { return "OmahaResponseHandlerAction"; }
@@ -59,6 +60,9 @@
   // set to non-empty in unit tests
   std::string boot_device_;
   
+  // The install plan, if we have an update.
+  InstallPlan install_plan_;
+  
   // True only if we got a response and the response said no updates
   bool got_no_update_response_;