[Extensions] Sync the 'allowed scripting on all urls' preference

sync/protocol/extension_specifics.proto

Index: sync/protocol/extension_specifics.proto
diff --git a/sync/protocol/extension_specifics.proto b/sync/protocol/extension_specifics.proto
index 2ef3f25c008843a6caae703e9c5ef312ca5d220b..586d279525a20c366288f88577a9fdf1ff2937fb 100644
--- a/sync/protocol/extension_specifics.proto
+++ b/sync/protocol/extension_specifics.proto
@@ -42,5 +42,9 @@ message ExtensionSpecifics {
 
   // Whether this extension was installed by the custodian of a supervised user.
   optional bool installed_by_custodian = 8;
+
+  // Whether this extension has explicit user consent access to all urls. This
+  // may not be present if the user hasn't given an explicit preference!

[not at google - send to devlin, 2015/02/11 01:34:51]

I would own up to what this is, a tri-state boolean - i.e. idiomatically
optional, whereas most fields are pragmatically optional (e.g. |name| isn't
*really* optional). And, why.

[Devlin, 2015/02/11 17:52:21]

Done.

+  optional bool all_urls_enabled = 9;
 }