login: Add --oobe-bootstrapping-slave flag to ChromeBit (veyron_mickey).

This change is meant for M49. The bootstrapping feature (a ChromeOS device is capable of being enrolled into a domain automatically
via Bluetooth) should have been enabled by default in M49. However, currently we accidently keep the feature behind a command switch.
So we decided to add a command switch to ChromeBit only and merge it into M49. After that, we'll enable the feature by default in M50
and later.

BUG=None
TEST=Run image on device and check the command switch in chrome://version page.

Change-Id: I4414534d85b53dd1365661aa2eb9781aef7d66a9
Reviewed-on: https://chromium-review.googlesource.com/335282
Trybot-Ready: Xiaoqian Dai <xdai@chromium.org>
Tested-by: Xiaoqian Dai <xdai@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
diff --git a/login_manager/chrome_setup.cc b/login_manager/chrome_setup.cc
index fd69d95..5249d77 100644
--- a/login_manager/chrome_setup.cc
+++ b/login_manager/chrome_setup.cc
@@ -254,6 +254,12 @@
 void AddEnterpriseFlags(ChromiumCommandBuilder* builder) {
   builder->AddArg("--enterprise-enrollment-initial-modulus=14");
   builder->AddArg("--enterprise-enrollment-modulus-limit=18");
+
+  // This flag is only used in M49 to enable bootstrapping for ChromeBit. All
+  // Chrome OS devices will be eligible for bootstrapping starting from M50.
+  // TODO(xdai): Remove this after it's cherry-picked in M49.
+  if (builder->IsBoard("veyron_mickey"))
+    builder->AddArg("--oobe-bootstrapping-slave");
 }
 
 // Adds patterns to the --vmodule flag.