Make host pairing screen the first screen for shark requisition.

With --show-host-pairing-demo and remora requisition, we start on the host pairing screen instead of the network screen.

There's an issue with the host pairing screen not being ready to accept context changes.

This is a temporary fix to get the end to end flow working. dzhioev@ will land a sequence of patches that are better long term.

BUG=405150
TEST=manual

Review URL: https://codereview.chromium.org/562923002

Cr-Commit-Position: refs/heads/master@{#294513}

chrome/browser/chromeos/login/wizard_controller.cc

@@ -108,9 +108,14 @@ bool CanShowHIDDetectionScreen() {
         chromeos::switches::kDisableHIDDetectionOnOOBE);
 }
 
+// Checks if we are a remora waiting for a shark.
 bool ShouldShowHostPairingScreen() {
-  return CommandLine::ForCurrentProcess()->HasSwitch(
+  const bool is_remora =
+      g_browser_process->platform_part()->browser_policy_connector_chromeos()->
+      GetDeviceCloudPolicyManager()->IsRemoraRequisition();
+  const bool pairing_demo = CommandLine::ForCurrentProcess()->HasSwitch(
       chromeos::switches::kShowHostPairingDemo);
+  return is_remora && pairing_demo;
 }
 
 bool IsResumableScreen(const std::string& screen) {
@@ -261,9 +266,11 @@ void WizardController::Init(
     }
   }
 
+  // Use the saved screen preference from Local State.
   const std::string screen_pref =
       GetLocalState()->GetString(prefs::kOobeScreenPending);
-  if (is_out_of_box_ && !screen_pref.empty() && (first_screen_name.empty() ||
+  if (is_out_of_box_ && !screen_pref.empty() &&
+      !ShouldShowHostPairingScreen() && (first_screen_name.empty() ||
       first_screen_name == WizardController::kTestNoScreenName)) {
     first_screen_name_ = screen_pref;
   }
@@ -572,8 +579,6 @@ void WizardController::OnUpdateCompleted() {
 
   if (is_shark) {
     ShowControllerPairingScreen();
-  } else if (ShouldShowHostPairingScreen()) {
-    ShowHostPairingScreen();
   } else if (!auth_token_.empty()) {
     // TODO(achuith): There is an issue with the auto enrollment check and
     // remote enrollment. crbug.com/403147.
@@ -898,7 +903,9 @@ void WizardController::AdvanceToScreen(const std::string& screen_name) {
   } else if (screen_name != kTestNoScreenName) {
     if (is_out_of_box_) {
       time_oobe_started_ = base::Time::Now();
-      if (CanShowHIDDetectionScreen()) {
+      if (ShouldShowHostPairingScreen()) {
+        ShowHostPairingScreen();
+      } else if (CanShowHIDDetectionScreen()) {
         base::Callback<void(bool)> on_check = base::Bind(
             &WizardController::OnHIDScreenNecessityCheck,
             weak_factory_.GetWeakPtr());