Make 'doc' available to group initializer.

common/content/mappings.js

@@ -119,9 +119,12 @@ var Map = Class("Map", {
                 .map(function ([i, prop]) [prop, this[i]], arguments)
                 .toObject();
 
-        args = update({ context: contexts.context },
-                      this.hive.argsExtra(args),
-                      args);
+        let orig = args;
+        args = update({
+                          context: contexts.context,
+                          doc: this.hive.group.lastDocument
+                      }, args);
+        update(args, this.hive.argsExtra(args), orig);
 
         let self = this;
         function repeat() self.action(args)

common/modules/base.jsm

@@ -611,12 +611,13 @@ function call(fn) {
  */
 function memoize(obj, key, getter) {
     if (arguments.length == 1) {
+        let res = Object.create(obj);
         for each (let prop in Object.getOwnPropertyNames(obj)) {
             let get = __lookupGetter__.call(obj, prop);
             if (get)
-                memoize(obj, prop, get);
+                memoize(res, prop, get);
         }
-        return obj;
+        return res;
     }
 
     try {

common/modules/contexts.jsm

@@ -25,6 +25,9 @@ var Group = Class("Group", {
         this.hives = [];
     },
 
+    set lastDocument(val) { this._lastDocument = val && Cu.getWeakReference(val); },
+    get lastDocument() this._lastDocument && this._lastDocument.get(),
+
     modifiable: true,
 
     cleanup: function cleanup() {
@@ -271,7 +274,7 @@ var Contexts = Module("contexts", {
         return frame;
     },
 
-    groups: Class.memoize(function () this.matchingGroups(this.modules.buffer.uri)),
+    groups: Class.memoize(function () this.matchingGroups()),
 
     allGroups: Class.memoize(function () Object.create(this.groupsProto, {
         groups: { value: this.initializedGroups() }
@@ -283,8 +286,14 @@ var Contexts = Module("contexts", {
 
     activeGroups: function (uri, doc) {
         if (!uri)
-            ({ uri, doc }) = this.modules.buffer;
-        return this.initializedGroups().filter(function (g) uri && g.filter(uri, doc));
+            var { uri, doc } = this.modules.buffer;
+
+        return this.initializedGroups().filter(function (g) {
+            let res = uri && g.filter(uri, doc);
+            if (doc)
+                g.lastDocument = res && doc;
+            return res;
+        });
     },
 
     flush: function flush() {