Make Meteor._WriteFence available on the client as well as the server…

…. Keep

Meteor._CurrentWriteFence on server only.

packages/livedata/livedata_server.js

@@ -442,6 +442,12 @@ _.extend(Meteor._LivedataSession.prototype, {
   }
 });
 
+// The current write fence. When there is a current write fence, code
+// that writes to databases should register their writes with it using
+// beginWrite().
+Meteor._CurrentWriteFence = new Meteor.EnvironmentVariable;
+
+
 /******************************************************************************/
 /* LivedataSubscription                                                       */
 /******************************************************************************/

packages/livedata/package.js

@@ -11,7 +11,7 @@ Package.on_use(function (api) {
   // manage the current set of subscriptions.
   api.use('minimongo', ['client', 'server']);
 
-  api.add_files('writefence.js', 'server');
+  api.add_files('writefence.js', ['client', 'server']);
   api.add_files('crossbar.js', 'server');
 
   api.add_files('livedata_common.js', ['client', 'server']);

packages/livedata/writefence.js

@@ -11,11 +11,6 @@ Meteor._WriteFence = function () {
   self.completion_callbacks = [];
 };
 
-// The current write fence. When there is a current write fence, code
-// that writes to databases should register their writes with it using
-// beginWrite().
-Meteor._CurrentWriteFence = new Meteor.EnvironmentVariable;
-
 _.extend(Meteor._WriteFence.prototype, {
   // Start tracking a write, and return an object to represent it. The
   // object has a single method, committed(). This method should be
@@ -62,6 +57,7 @@ _.extend(Meteor._WriteFence.prototype, {
   },
 
   // Convenience function. Arms the fence, then blocks until it fires.
+  // Only can be called on the server.
   armAndWait: function () {
     var self = this;
     var future = new Future;