Spark._currentRenderer not an EnvironmentVariable

This isn't the kind of dynamic var that should
persist into timer callbacks, it should just be
on the stack.  Also cuts dependence of spark
on dynamics.

admin/spark-standalone.sh

@@ -8,7 +8,6 @@ PACKAGES_DIR=`dirname $0`/../packages
 
 echo 'Meteor = {};'
 cat $PACKAGES_DIR/uuid/uuid.js
-cat $PACKAGES_DIR/meteor/dynamics_browser.js
 cat $PACKAGES_DIR/deps/deps.js
 cat $PACKAGES_DIR/liverange/liverange.js
 cat $PACKAGES_DIR/universal-events/listener.js

packages/spark/spark.js

@@ -29,7 +29,20 @@
 
 Spark = {};
 
-Spark._currentRenderer = new Meteor.EnvironmentVariable;
+Spark._currentRenderer = (function () {
+  var current = null;
+  return {
+    get: function () {
+      return current;
+    },
+    withValue: function (v, func) {
+      var previous = current;
+      current = v;
+      try { return func(); }
+      finally { current = previous; }
+    }
+  };
+})();
 
 Spark._TAG = "_spark_" + Meteor.uuid();
 // XXX document contract for each type of annotation?