Add a device setting that indicates dev mode blocking status.

chrome/browser/chromeos/policy/device_policy_decoder_chromeos.cc

Index: chrome/browser/chromeos/policy/device_policy_decoder_chromeos.cc
diff --git a/chrome/browser/chromeos/policy/device_policy_decoder_chromeos.cc b/chrome/browser/chromeos/policy/device_policy_decoder_chromeos.cc
index 0e740a637a3478dd5fbb53210b98cf75b1e2afe4..7856cff3def1758f22f793aac01e34b8ade8a271 100644
--- a/chrome/browser/chromeos/policy/device_policy_decoder_chromeos.cc
+++ b/chrome/browser/chromeos/policy/device_policy_decoder_chromeos.cc
@@ -769,6 +769,18 @@ void DecodeGenericPolicies(const em::ChromeDeviceSettingsProto& policy,
       }
     }
   }
+
+  if (policy.has_system_settings()) {
+    const em::SystemSettingsProto& container(policy.system_settings());
+    if (container.has_block_devmode()) {
+      policies->Set(
+          key::kDeviceBlockDevmode,
+          POLICY_LEVEL_MANDATORY,
+          POLICY_SCOPE_MACHINE,
+          new base::FundamentalValue(container.block_devmode()),
+          NULL);
+    }
+  }
 }
 
 }  // namespace