New policy to enable/disable HTTP-based downloads.

chrome/browser/policy/proto/chromeos/chrome_device_policy.proto

Index: chrome/browser/policy/proto/chromeos/chrome_device_policy.proto
diff --git a/chrome/browser/policy/proto/chromeos/chrome_device_policy.proto b/chrome/browser/policy/proto/chromeos/chrome_device_policy.proto
index 2c095dc5c21fe22c0f0f28ef7e146ce1cb7162cb..cce8f3292ae56ee3daad583d708e6e37c0112702 100644
--- a/chrome/browser/policy/proto/chromeos/chrome_device_policy.proto
+++ b/chrome/browser/policy/proto/chromeos/chrome_device_policy.proto
@@ -202,6 +202,9 @@ message AutoUpdateSettingsProto {
   // True if the device should reboot automatically when an update has been
   // applied and a reboot is required to complete the update process.
   optional bool reboot_after_update = 6;
+
+  // True if AU payloads can be downloaded via HTTP. False otherwise.
+  optional bool http_downloads_enabled = 7 [default = false];
 }
 
 message StartUpUrlsProto {