update_engine: Don't keep pointer to SystemState available objects

These objects are available thorugh SystemState. No need to keep pointer
to them in various classes (OmahaRequestBuilderXml in this case). This
makes testing/debugging easier because there will be one central
location for getting pointers to these values.

BUG=b:171829801
TEST=cros_workon_make --board reef --test update_engine

Change-Id: I02a36afdc7dcb00e02b1a61263141745afc7fb26
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2543814
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Commit-Queue: Amin Hassani <ahassani@chromium.org>
diff --git a/cros/omaha_request_action.cc b/cros/omaha_request_action.cc
index 6f270c0..f847194 100644
--- a/cros/omaha_request_action.cc
+++ b/cros/omaha_request_action.cc
@@ -456,19 +456,17 @@
     return;
   }
 
-  auto* params = SystemState::Get()->request_params();
   OmahaRequestBuilderXml omaha_request(event_.get(),
-                                       params,
                                        ping_only_,
                                        ShouldPing(),  // include_ping
                                        ping_active_days_,
                                        ping_roll_call_days_,
                                        GetInstallDate(),
-                                       SystemState::Get()->prefs(),
                                        session_id_);
   string request_post = omaha_request.GetRequest();
 
   // Set X-Goog-Update headers.
+  const auto* params = SystemState::Get()->request_params();
   http_fetcher_->SetHeader(kXGoogleUpdateInteractivity,
                            params->interactive() ? "fg" : "bg");
   http_fetcher_->SetHeader(kXGoogleUpdateAppId, params->GetAppId());