Handle case where PointerGestures is loaded asynchronously

Part of Polymer/platform-dev#11

build.json

@@ -8,5 +8,6 @@
   "src/track.js",
   "src/flick.js",
   "src/pinch.js",
-  "src/tap.js"
+  "src/tap.js",
+  "src/registerScopes.js"
 ]

src/dispatcher.js

@@ -206,9 +206,11 @@
     }
   };
   dispatcher.boundHandler = dispatcher.eventHandler.bind(dispatcher);
+  // recognizers call into the dispatcher and load later
+  // solve the chicken and egg problem by having registerScopes module run last
+  dispatcher.registerQueue = [];
+  dispatcher.immediateRegister = false;
   scope.dispatcher = dispatcher;
-  var registerQueue = [];
-  var immediateRegister = false;
   /**
    * Enable gesture events for a given scope, typically
    * [ShadowRoots](https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/shadow/index.html#shadow-root-object).
@@ -219,20 +221,15 @@
    * support on.
    */
   scope.register = function(inScope) {
-    if (immediateRegister) {
+    if (dispatcher.immediateRegister) {
       var pe = window.PointerEventsPolyfill;
       if (pe) {
         pe.register(inScope);
       }
       scope.dispatcher.registerTarget(inScope);
     } else {
-      registerQueue.push(inScope);
+      dispatcher.registerQueue.push(inScope);
     }
   };
-  // wait to register scopes until recognizers load
-  document.addEventListener('DOMContentLoaded', function() {
-    immediateRegister = true;
-    registerQueue.push(document);
-    registerQueue.forEach(scope.register);
-  });
+  scope.register(document);
 })(window.PointerGestures);

src/registerScopes.js

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2013 The Polymer Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file.
+ */
+
+/**
+ * Because recognizers are loaded after dispatcher, we have to wait to register
+ * scopes until after all the recognizers.
+ */
+(function(scope) {
+  var dispatcher = scope.dispatcher;
+  function registerScopes() {
+    dispatcher.immediateRegister = true;
+    var rq = dispatcher.registerQueue;
+    rq.forEach(scope.register);
+    rq.length = 0;
+  }
+  if (document.readyState === 'complete') {
+    registerScopes();
+  } else {
+    // register scopes after a steadystate is reached
+    // less MutationObserver churn
+    document.addEventListener('readystatechange', function() {
+      if (document.readyState === 'complete') {
+        registerScopes();
+      }
+    });
+  }
+})(window.PointerGestures);