Adding polyfill support for custom elements.

pkg/custom_element/lib/custom-elements.debug.js

Index: pkg/custom_element/lib/custom-elements.debug.js
diff --git a/pkg/custom_element/lib/custom-elements.debug.js b/pkg/custom_element/lib/custom-elements.debug.js
new file mode 100644
index 0000000000000000000000000000000000000000..400730bea18f9f5335e2fc5d818fb82ccaa94d43
--- /dev/null
+++ b/pkg/custom_element/lib/custom-elements.debug.js
@@ -0,0 +1,1458 @@
+// Copyright (c) 2012 The Polymer Authors. All rights reserved.

[Jennifer Messerly, 2013/08/20 19:09:59]

from the comment on earlier CL's, should this be named:

    custom_element.js
    custom_element.min.js

basically, no "debug" and also use underscores to match Dart file naming
conventions. (Shadow DOM pkg also uses underscores. It uses .debug too, but I
think we were going to fix that...)

[blois, 2013/08/20 19:36:56]

My goal was that the file can be copied over from Polymer with no modifications-
naming style is from their file. The .debug portion is because the unadorned
name is the version which uses the loaders.

+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+(function() {
+
+var scope = window.PolymerLoader = {};
+var flags = {};
+
+// convert url arguments to flags
+
+if (!flags.noOpts) {
+  location.search.slice(1).split('&').forEach(function(o) {
+    o = o.split('=');
+    o[0] && (flags[o[0]] = o[1] || true);
+  });
+}
+
+// process global logFlags
+
+parseLogFlags(flags);
+
+function load(scopeName) {
+  // imports
+
+  var scope = window[scopeName];
+  var entryPointName = scope.entryPointName;
+  var processFlags = scope.processFlags;
+
+  // acquire attributes and base path from entry point
+
+  var entryPoint = findScript(entryPointName);
+  var base = entryPoint.basePath;
+
+  // acquire common flags
+  var flags = scope.flags;
+
+  // convert attributes to flags
+  var flags = PolymerLoader.flags;
+  for (var i=0, a; (a=entryPoint.attributes[i]); i++) {
+    if (a.name !== 'src') {
+      flags[a.name] = a.value || true;
+    }
+  }
+
+  // parse log flags into global
+  parseLogFlags(flags);
+
+  // exports
+
+  scope.basePath = base;
+  scope.flags = flags;
+
+  // process flags for dynamic dependencies
+
+  if (processFlags) {
+    processFlags.call(scope, flags);
+  }
+
+  // post-process imports
+
+  var modules = scope.modules || [];
+  var sheets = scope.sheets || [];
+
+  // write script tags for dependencies
+
+  modules.forEach(function(src) {
+    document.write('<script src="' + base + src + '"></script>');
+  });
+
+  // write link tags for styles
+
+  sheets.forEach(function(src) {
+    document.write('<link rel="stylesheet" href="' + base + src + '">');
+  });
+}
+
+// utility method
+
+function findScript(fileName) {
+  var script = document.querySelector('script[src*="' + fileName + '"]');
+  var src = script.attributes.src.value;
+  script.basePath = src.slice(0, src.indexOf(fileName));
+  return script;
+}
+
+function parseLogFlags(flags) {
+  var logFlags = window.logFlags = window.logFlags || {};
+  if (flags.log) {
+    flags.log.split(',').forEach(function(f) {
+      logFlags[f] = true;
+    });
+  }
+}
+
+scope.flags = flags;
+scope.load = load;
+
+})();
+
+window.CustomElements = {flags:{}};
+// SideTable is a weak map where possible. If WeakMap is not available the
+// association is stored as an expando property.
+var SideTable;
+// TODO(arv): WeakMap does not allow for Node etc to be keys in Firefox
+if (typeof WeakMap !== 'undefined' && navigator.userAgent.indexOf('Firefox/') < 0) {
+  SideTable = WeakMap;
+} else {
+  (function() {
+    var defineProperty = Object.defineProperty;
+    var hasOwnProperty = Object.hasOwnProperty;
+    var counter = new Date().getTime() % 1e9;
+
+    SideTable = function() {
+      this.name = '__st' + (Math.random() * 1e9 >>> 0) + (counter++ + '__');
+    };
+
+    SideTable.prototype = {
+      set: function(key, value) {
+        defineProperty(key, this.name, {value: value, writable: true});
+      },
+      get: function(key) {
+        return hasOwnProperty.call(key, this.name) ? key[this.name] : undefined;
+      },
+      delete: function(key) {
+        this.set(key, undefined);
+      }
+    }
+  })();
+}
+
+(function(global) {
+
+  var registrationsTable = new SideTable();
+
+  // We use setImmediate or postMessage for our future callback.
+  var setImmediate = window.msSetImmediate;
+
+  // Use post message to emulate setImmediate.
+  if (!setImmediate) {
+    var setImmediateQueue = [];
+    var sentinel = String(Math.random());
+    window.addEventListener('message', function(e) {
+      if (e.data === sentinel) {
+        var queue = setImmediateQueue;
+        setImmediateQueue = [];
+        queue.forEach(function(func) {
+          func();
+        });
+      }
+    });
+    setImmediate = function(func) {
+      setImmediateQueue.push(func);
+      window.postMessage(sentinel, '*');
+    };
+  }
+
+  // This is used to ensure that we never schedule 2 callas to setImmediate
+  var isScheduled = false;
+
+  // Keep track of observers that needs to be notified next time.
+  var scheduledObservers = [];
+
+  /**
+   * Schedules |dispatchCallback| to be called in the future.
+   * @param {MutationObserver} observer
+   */
+  function scheduleCallback(observer) {
+    scheduledObservers.push(observer);
+    if (!isScheduled) {
+      isScheduled = true;
+      setImmediate(dispatchCallbacks);
+    }
+  }
+
+  function wrapIfNeeded(node) {
+    return window.ShadowDOMPolyfill &&
+        window.ShadowDOMPolyfill.wrapIfNeeded(node) ||
+        node;
+  }
+
+  function dispatchCallbacks() {
+    // http://dom.spec.whatwg.org/#mutation-observers
+
+    isScheduled = false; // Used to allow a new setImmediate call above.
+
+    var observers = scheduledObservers;
+    scheduledObservers = [];
+    // Sort observers based on their creation UID (incremental).
+    observers.sort(function(o1, o2) {
+      return o1.uid_ - o2.uid_;
+    });
+
+    var anyNonEmpty = false;
+    observers.forEach(function(observer) {
+
+      // 2.1, 2.2
+      var queue = observer.takeRecords();
+      // 2.3. Remove all transient registered observers whose observer is mo.
+      removeTransientObserversFor(observer);
+
+      // 2.4
+      if (queue.length) {
+        observer.callback_(queue, observer);
+        anyNonEmpty = true;
+      }
+    });
+
+    // 3.
+    if (anyNonEmpty)
+      dispatchCallbacks();
+  }
+
+  function removeTransientObserversFor(observer) {
+    observer.nodes_.forEach(function(node) {
+      var registrations = registrationsTable.get(node);
+      if (!registrations)
+        return;
+      registrations.forEach(function(registration) {
+        if (registration.observer === observer)
+          registration.removeTransientObservers();
+      });
+    });
+  }
+
+  /**
+   * This function is used for the "For each registered observer observer (with
+   * observer's options as options) in target's list of registered observers,
+   * run these substeps:" and the "For each ancestor ancestor of target, and for
+   * each registered observer observer (with options options) in ancestor's list
+   * of registered observers, run these substeps:" part of the algorithms. The
+   * |options.subtree| is checked to ensure that the callback is called
+   * correctly.
+   *
+   * @param {Node} target
+   * @param {function(MutationObserverInit):MutationRecord} callback
+   */
+  function forEachAncestorAndObserverEnqueueRecord(target, callback) {
+    for (var node = target; node; node = node.parentNode) {
+      var registrations = registrationsTable.get(node);
+
+      if (registrations) {
+        for (var j = 0; j < registrations.length; j++) {
+          var registration = registrations[j];
+          var options = registration.options;
+
+          // Only target ignores subtree.
+          if (node !== target && !options.subtree)
+            continue;
+
+          var record = callback(options);
+          if (record)
+            registration.enqueue(record);
+        }
+      }
+    }
+  }
+
+  var uidCounter = 0;
+
+  /**
+   * The class that maps to the DOM MutationObserver interface.
+   * @param {Function} callback.
+   * @constructor
+   */
+  function JsMutationObserver(callback) {
+    this.callback_ = callback;
+    this.nodes_ = [];
+    this.records_ = [];
+    this.uid_ = ++uidCounter;
+  }
+
+  JsMutationObserver.prototype = {
+    observe: function(target, options) {
+      target = wrapIfNeeded(target);
+
+      // 1.1
+      if (!options.childList && !options.attributes && !options.characterData ||
+
+          // 1.2
+          options.attributeOldValue && !options.attributes ||
+
+          // 1.3
+          options.attributeFilter && options.attributeFilter.length &&
+              !options.attributes ||
+
+          // 1.4
+          options.characterDataOldValue && !options.characterData) {
+
+        throw new SyntaxError();
+      }
+
+      var registrations = registrationsTable.get(target);
+      if (!registrations)
+        registrationsTable.set(target, registrations = []);
+
+      // 2
+      // If target's list of registered observers already includes a registered
+      // observer associated with the context object, replace that registered
+      // observer's options with options.
+      var registration;
+      for (var i = 0; i < registrations.length; i++) {
+        if (registrations[i].observer === this) {
+          registration = registrations[i];
+          registration.removeListeners();
+          registration.options = options;
+          break;
+        }
+      }
+
+      // 3.
+      // Otherwise, add a new registered observer to target's list of registered
+      // observers with the context object as the observer and options as the
+      // options, and add target to context object's list of nodes on which it
+      // is registered.
+      if (!registration) {
+        registration = new Registration(this, target, options);
+        registrations.push(registration);
+        this.nodes_.push(target);
+      }
+
+      registration.addListeners();
+    },
+
+    disconnect: function() {
+      this.nodes_.forEach(function(node) {
+        var registrations = registrationsTable.get(node);
+        for (var i = 0; i < registrations.length; i++) {
+          var registration = registrations[i];
+          if (registration.observer === this) {
+            registration.removeListeners();
+            registrations.splice(i, 1);
+            // Each node can only have one registered observer associated with
+            // this observer.
+            break;
+          }
+        }
+      }, this);
+      this.records_ = [];
+    },
+
+    takeRecords: function() {
+      var copyOfRecords = this.records_;
+      this.records_ = [];
+      return copyOfRecords;
+    }
+  };
+
+  /**
+   * @param {string} type
+   * @param {Node} target
+   * @constructor
+   */
+  function MutationRecord(type, target) {
+    this.type = type;
+    this.target = target;
+    this.addedNodes = [];
+    this.removedNodes = [];
+    this.previousSibling = null;
+    this.nextSibling = null;
+    this.attributeName = null;
+    this.attributeNamespace = null;
+    this.oldValue = null;
+  }
+
+  function copyMutationRecord(original) {
+    var record = new MutationRecord(original.type, original.target);
+    record.addedNodes = original.addedNodes.slice();
+    record.removedNodes = original.removedNodes.slice();
+    record.previousSibling = original.previousSibling;
+    record.nextSibling = original.nextSibling;
+    record.attributeName = original.attributeName;
+    record.attributeNamespace = original.attributeNamespace;
+    record.oldValue = original.oldValue;
+    return record;
+  };
+
+  // We keep track of the two (possibly one) records used in a single mutation.
+  var currentRecord, recordWithOldValue;
+
+  /**
+   * Creates a record without |oldValue| and caches it as |currentRecord| for
+   * later use.
+   * @param {string} oldValue
+   * @return {MutationRecord}
+   */
+  function getRecord(type, target) {
+    return currentRecord = new MutationRecord(type, target);
+  }
+
+  /**
+   * Gets or creates a record with |oldValue| based in the |currentRecord|
+   * @param {string} oldValue
+   * @return {MutationRecord}
+   */
+  function getRecordWithOldValue(oldValue) {
+    if (recordWithOldValue)
+      return recordWithOldValue;
+    recordWithOldValue = copyMutationRecord(currentRecord);
+    recordWithOldValue.oldValue = oldValue;
+    return recordWithOldValue;
+  }
+
+  function clearRecords() {
+    currentRecord = recordWithOldValue = undefined;
+  }
+
+  /**
+   * @param {MutationRecord} record
+   * @return {boolean} Whether the record represents a record from the current
+   * mutation event.
+   */
+  function recordRepresentsCurrentMutation(record) {
+    return record === recordWithOldValue || record === currentRecord;
+  }
+
+  /**
+   * Selects which record, if any, to replace the last record in the queue.
+   * This returns |null| if no record should be replaced.
+   *
+   * @param {MutationRecord} lastRecord
+   * @param {MutationRecord} newRecord
+   * @param {MutationRecord}
+   */
+  function selectRecord(lastRecord, newRecord) {
+    if (lastRecord === newRecord)
+      return lastRecord;
+
+    // Check if the the record we are adding represents the same record. If
+    // so, we keep the one with the oldValue in it.
+    if (recordWithOldValue && recordRepresentsCurrentMutation(lastRecord))
+      return recordWithOldValue;
+
+    return null;
+  }
+
+  /**
+   * Class used to represent a registered observer.
+   * @param {MutationObserver} observer
+   * @param {Node} target
+   * @param {MutationObserverInit} options
+   * @constructor
+   */
+  function Registration(observer, target, options) {
+    this.observer = observer;
+    this.target = target;
+    this.options = options;
+    this.transientObservedNodes = [];
+  }
+
+  Registration.prototype = {
+    enqueue: function(record) {
+      var records = this.observer.records_;
+      var length = records.length;
+
+      // There are cases where we replace the last record with the new record.
+      // For example if the record represents the same mutation we need to use
+      // the one with the oldValue. If we get same record (this can happen as we
+      // walk up the tree) we ignore the new record.
+      if (records.length > 0) {
+        var lastRecord = records[length - 1];
+        var recordToReplaceLast = selectRecord(lastRecord, record);
+        if (recordToReplaceLast) {
+          records[length - 1] = recordToReplaceLast;
+          return;
+        }
+      } else {
+        scheduleCallback(this.observer);
+      }
+
+      records[length] = record;
+    },
+
+    addListeners: function() {
+      this.addListeners_(this.target);
+    },
+
+    addListeners_: function(node) {
+      var options = this.options;
+      if (options.attributes)
+        node.addEventListener('DOMAttrModified', this, true);
+
+      if (options.characterData)
+        node.addEventListener('DOMCharacterDataModified', this, true);
+
+      if (options.childList)
+        node.addEventListener('DOMNodeInserted', this, true);
+
+      if (options.childList || options.subtree)
+        node.addEventListener('DOMNodeRemoved', this, true);
+    },
+
+    removeListeners: function() {
+      this.removeListeners_(this.target);
+    },
+
+    removeListeners_: function(node) {
+      var options = this.options;
+      if (options.attributes)
+        node.removeEventListener('DOMAttrModified', this, true);
+
+      if (options.characterData)
+        node.removeEventListener('DOMCharacterDataModified', this, true);
+
+      if (options.childList)
+        node.removeEventListener('DOMNodeInserted', this, true);
+
+      if (options.childList || options.subtree)
+        node.removeEventListener('DOMNodeRemoved', this, true);
+    },
+
+    /**
+     * Adds a transient observer on node. The transient observer gets removed
+     * next time we deliver the change records.
+     * @param {Node} node
+     */
+    addTransientObserver: function(node) {
+      // Don't add transient observers on the target itself. We already have all
+      // the required listeners set up on the target.
+      if (node === this.target)
+        return;
+
+      this.addListeners_(node);
+      this.transientObservedNodes.push(node);
+      var registrations = registrationsTable.get(node);
+      if (!registrations)
+        registrationsTable.set(node, registrations = []);
+
+      // We know that registrations does not contain this because we already
+      // checked if node === this.target.
+      registrations.push(this);
+    },
+
+    removeTransientObservers: function() {
+      var transientObservedNodes = this.transientObservedNodes;
+      this.transientObservedNodes = [];
+
+      transientObservedNodes.forEach(function(node) {
+        // Transient observers are never added to the target.
+        this.removeListeners_(node);
+
+        var registrations = registrationsTable.get(node);
+        for (var i = 0; i < registrations.length; i++) {
+          if (registrations[i] === this) {
+            registrations.splice(i, 1);
+            // Each node can only have one registered observer associated with
+            // this observer.
+            break;
+          }
+        }
+      }, this);
+    },
+
+    handleEvent: function(e) {
+      // Stop propagation since we are managing the propagation manually.
+      // This means that other mutation events on the page will not work
+      // correctly but that is by design.
+      e.stopImmediatePropagation();
+
+      switch (e.type) {
+        case 'DOMAttrModified':
+          // http://dom.spec.whatwg.org/#concept-mo-queue-attributes
+
+          var name = e.attrName;
+          var namespace = e.relatedNode.namespaceURI;
+          var target = e.target;
+
+          // 1.
+          var record = new getRecord('attributes', target);
+          record.attributeName = name;
+          record.attributeNamespace = namespace;
+
+          // 2.
+          var oldValue =
+              e.attrChange === MutationEvent.ADDITION ? null : e.prevValue;
+
+          forEachAncestorAndObserverEnqueueRecord(target, function(options) {
+            // 3.1, 4.2
+            if (!options.attributes)
+              return;
+
+            // 3.2, 4.3
+            if (options.attributeFilter && options.attributeFilter.length &&
+                options.attributeFilter.indexOf(name) === -1 &&
+                options.attributeFilter.indexOf(namespace) === -1) {
+              return;
+            }
+            // 3.3, 4.4
+            if (options.attributeOldValue)
+              return getRecordWithOldValue(oldValue);
+
+            // 3.4, 4.5
+            return record;
+          });
+
+          break;
+
+        case 'DOMCharacterDataModified':
+          // http://dom.spec.whatwg.org/#concept-mo-queue-characterdata
+          var target = e.target;
+
+          // 1.
+          var record = getRecord('characterData', target);
+
+          // 2.
+          var oldValue = e.prevValue;
+
+
+          forEachAncestorAndObserverEnqueueRecord(target, function(options) {
+            // 3.1, 4.2
+            if (!options.characterData)
+              return;
+
+            // 3.2, 4.3
+            if (options.characterDataOldValue)
+              return getRecordWithOldValue(oldValue);
+
+            // 3.3, 4.4
+            return record;
+          });
+
+          break;
+
+        case 'DOMNodeRemoved':
+          this.addTransientObserver(e.target);
+          // Fall through.
+        case 'DOMNodeInserted':
+          // http://dom.spec.whatwg.org/#concept-mo-queue-childlist
+          var target = e.relatedNode;
+          var changedNode = e.target;
+          var addedNodes, removedNodes;
+          if (e.type === 'DOMNodeInserted') {
+            addedNodes = [changedNode];
+            removedNodes = [];
+          } else {
+
+            addedNodes = [];
+            removedNodes = [changedNode];
+          }
+          var previousSibling = changedNode.previousSibling;
+          var nextSibling = changedNode.nextSibling;
+
+          // 1.
+          var record = getRecord('childList', target);
+          record.addedNodes = addedNodes;
+          record.removedNodes = removedNodes;
+          record.previousSibling = previousSibling;
+          record.nextSibling = nextSibling;
+
+          forEachAncestorAndObserverEnqueueRecord(target, function(options) {
+            // 2.1, 3.2
+            if (!options.childList)
+              return;
+
+            // 2.2, 3.3
+            return record;
+          });
+
+      }
+
+      clearRecords();
+    }
+  };
+
+  global.JsMutationObserver = JsMutationObserver;
+
+})(this);
+
+if (!window.MutationObserver) {
+  window.MutationObserver =
+      window.WebKitMutationObserver ||
+      window.JsMutationObserver;
+  if (!MutationObserver) {
+    throw new Error("no mutation observer support");
+  }
+}
+
+(function(scope){
+
+/*
+if (HTMLElement.prototype.webkitShadowRoot) {
+  Object.defineProperty(HTMLElement.prototype, 'shadowRoot', {
+    get: function() {
+      return this.webkitShadowRoot;
+    }
+  };
+}
+*/
+
+// walk the subtree rooted at node, applying 'find(element, data)' function
+// to each element
+// if 'find' returns true for 'element', do not search element's subtree
+function findAll(node, find, data) {
+  var e = node.firstElementChild;
+  if (!e) {
+    e = node.firstChild;
+    while (e && e.nodeType !== Node.ELEMENT_NODE) {
+      e = e.nextSibling;
+    }
+  }
+  while (e) {
+    if (find(e, data) !== true) {
+      findAll(e, find, data);
+    }
+    e = e.nextElementSibling;
+  }
+  return null;
+}
+
+// walk all shadowRoots on a given node.
+function forRoots(node, cb) {
+  var root = node.webkitShadowRoot;
+  while(root) {
+    forSubtree(root, cb);
+    root = root.olderShadowRoot;
+  }
+}
+
+// walk the subtree rooted at node, including descent into shadow-roots,
+// applying 'cb' to each element
+function forSubtree(node, cb) {
+  //logFlags.dom && node.childNodes && node.childNodes.length && console.group('subTree: ', node);
+  findAll(node, function(e) {
+    if (cb(e)) {
+      return true;
+    }
+    forRoots(e, cb);
+  });
+  forRoots(node, cb);
+  //logFlags.dom && node.childNodes && node.childNodes.length && console.groupEnd();
+}
+
+// manage lifecycle on added node
+function added(node) {
+  if (upgrade(node)) {
+    insertedNode(node);
+    return true;
+  }
+  inserted(node);
+}
+
+// manage lifecycle on added node's subtree only
+function addedSubtree(node) {
+  forSubtree(node, function(e) {
+    if (added(e)) {
+      return true;
+    }
+  });
+}
+
+// manage lifecycle on added node and it's subtree
+function addedNode(node) {
+  return added(node) || addedSubtree(node);
+}
+
+// upgrade custom elements at node, if applicable
+function upgrade(node) {
+  if (!node.__upgraded__ && node.nodeType === Node.ELEMENT_NODE) {
+    var type = node.getAttribute('is') || node.localName;
+    var definition = scope.registry[type];
+    if (definition) {
+      logFlags.dom && console.group('upgrade:', node.localName);
+      scope.upgrade(node);
+      logFlags.dom && console.groupEnd();
+      return true;
+    }
+  }
+}
+
+function insertedNode(node) {
+  inserted(node);
+  if (inDocument(node)) {
+    forSubtree(node, function(e) {
+      inserted(e);
+    });
+  }
+}
+
+// TODO(sjmiles): if there are descents into trees that can never have inDocument(*) true, fix this
+
+function inserted(element) {
+  // TODO(sjmiles): it's possible we were inserted and removed in the space
+  // of one microtask, in which case we won't be 'inDocument' here
+  // But there are other cases where we are testing for inserted without
+  // specific knowledge of mutations, and must test 'inDocument' to determine
+  // whether to call inserted
+  // If we can factor these cases into separate code paths we can have
+  // better diagnostics.
+  // TODO(sjmiles): when logging, do work on all custom elements so we can
+  // track behavior even when callbacks not defined
+  //console.log('inserted: ', element.localName);
+  if (element.enteredDocumentCallback || (element.__upgraded__ && logFlags.dom)) {
+    logFlags.dom && console.group('inserted:', element.localName);
+    if (inDocument(element)) {
+      element.__inserted = (element.__inserted || 0) + 1;
+      // if we are in a 'removed' state, bluntly adjust to an 'inserted' state
+      if (element.__inserted < 1) {
+        element.__inserted = 1;
+      }
+      // if we are 'over inserted', squelch the callback
+      if (element.__inserted > 1) {
+        logFlags.dom && console.warn('inserted:', element.localName,
+          'insert/remove count:', element.__inserted)
+      } else if (element.enteredDocumentCallback) {
+        logFlags.dom && console.log('inserted:', element.localName);
+        element.enteredDocumentCallback();
+      }
+    }
+    logFlags.dom && console.groupEnd();
+  }
+}
+
+function removedNode(node) {
+  removed(node);
+  forSubtree(node, function(e) {
+    removed(e);
+  });
+}
+
+function removed(element) {
+  // TODO(sjmiles): temporary: do work on all custom elements so we can track
+  // behavior even when callbacks not defined
+  if (element.leftDocumentCallback || (element.__upgraded__ && logFlags.dom)) {
+    logFlags.dom && console.log('removed:', element.localName);
+    if (!inDocument(element)) {
+      element.__inserted = (element.__inserted || 0) - 1;
+      // if we are in a 'inserted' state, bluntly adjust to an 'removed' state
+      if (element.__inserted > 0) {
+        element.__inserted = 0;
+      }
+      // if we are 'over removed', squelch the callback
+      if (element.__inserted < 0) {
+        logFlags.dom && console.warn('removed:', element.localName,
+            'insert/remove count:', element.__inserted)
+      } else if (element.leftDocumentCallback) {
+        element.leftDocumentCallback();
+      }
+    }
+  }
+}
+
+function inDocument(element) {
+  var p = element;
+  while (p) {
+    if (p == element.ownerDocument) {
+      return true;
+    }
+    p = p.parentNode || p.host;
+  }
+}
+
+function watchShadow(node) {
+  if (node.webkitShadowRoot && !node.webkitShadowRoot.__watched) {
+    logFlags.dom && console.log('watching shadow-root for: ', node.localName);
+    // watch all unwatched roots...
+    var root = node.webkitShadowRoot;
+    while (root) {
+      watchRoot(root);
+      root = root.olderShadowRoot;
+    }
+  }
+}
+
+function watchRoot(root) {
+  if (!root.__watched) {
+    observe(root);
+    root.__watched = true;
+  }
+}
+
+function watchAllShadows(node) {
+  watchShadow(node);
+  forSubtree(node, function(e) {
+    watchShadow(node);
+  });
+}
+
+function filter(inNode) {
+  switch (inNode.localName) {
+    case 'style':
+    case 'script':
+    case 'template':
+    case undefined:
+      return true;
+  }
+}
+
+function handler(mutations) {
+  //
+  if (logFlags.dom) {
+    var mx = mutations[0];
+    if (mx && mx.type === 'childList' && mx.addedNodes) {
+        if (mx.addedNodes) {
+          var d = mx.addedNodes[0];
+          while (d && d !== document && !d.host) {
+            d = d.parentNode;
+          }
+          var u = d && (d.URL || d._URL || (d.host && d.host.localName)) || '';
+          u = u.split('/?').shift().split('/').pop();
+        }
+    }
+    console.group('mutations (%d) [%s]', mutations.length, u || '');
+  }
+  //
+  mutations.forEach(function(mx) {
+    //logFlags.dom && console.group('mutation');
+    if (mx.type === 'childList') {
+      forEach(mx.addedNodes, function(n) {
+        //logFlags.dom && console.log(n.localName);
+        if (filter(n)) {
+          return;
+        }
+        // watch shadow-roots on nodes that have had them attached manually
+        // TODO(sjmiles): remove if createShadowRoot is overridden
+        // TODO(sjmiles): removed as an optimization, manual shadow roots
+        // must be watched explicitly
+        //watchAllShadows(n);
+        // nodes added may need lifecycle management
+        addedNode(n);
+      });
+      // removed nodes may need lifecycle management
+      forEach(mx.removedNodes, function(n) {
+        //logFlags.dom && console.log(n.localName);
+        if (filter(n)) {
+          return;
+        }
+        removedNode(n);
+      });
+    }
+    //logFlags.dom && console.groupEnd();
+  });
+  logFlags.dom && console.groupEnd();
+};
+
+var observer = new MutationObserver(handler);
+
+function takeRecords() {
+  // TODO(sjmiles): ask Raf why we have to call handler ourselves
+  handler(observer.takeRecords());
+}
+
+var forEach = Array.prototype.forEach.call.bind(Array.prototype.forEach);
+
+function observe(inRoot) {
+  observer.observe(inRoot, {childList: true, subtree: true});
+}
+
+function observeDocument(document) {
+  observe(document);
+}
+
+function upgradeDocument(document) {
+  logFlags.dom && console.group('upgradeDocument: ', (document.URL || document._URL || '').split('/').pop());
+  addedNode(document);
+  logFlags.dom && console.groupEnd();
+}
+
+// exports
+
+scope.watchShadow = watchShadow;
+scope.watchAllShadows = watchAllShadows;
+
+scope.upgradeAll = addedNode;
+scope.upgradeSubtree = addedSubtree;
+
+scope.observeDocument = observeDocument;
+scope.upgradeDocument = upgradeDocument;
+
+scope.takeRecords = takeRecords;
+
+})(window.CustomElements);
+
+/**
+ * Implements `document.register`
+ * @module CustomElements
+*/
+
+/**
+ * Polyfilled extensions to the `document` object.
+ * @class Document
+*/
+
+(function(scope) {
+
+// imports
+
+if (!scope) {
+  scope = window.CustomElements = {flags:{}};
+}
+var flags = scope.flags;
+
+// native document.register?
+
+var hasNative = Boolean(document.webkitRegister || document.register);
+var useNative = !flags.register && hasNative;
+
+if (useNative) {
+
+  // normalize
+  document.register = document.register || document.webkitRegister;
+
+  // stub
+  var nop = function() {};
+
+  // exports
+  scope.registry = {};
+  scope.upgradeElement = nop;
+
+  scope.watchShadow = nop;
+  scope.watchAllShadows = nop;
+  scope.upgrade = nop;
+  scope.upgradeAll = nop;
+  scope.upgradeSubtree = nop;
+  scope.observeDocument = nop;
+  scope.upgradeDocument = nop;
+  scope.takeRecords = nop;
+
+} else {
+
+  /**
+   * Registers a custom tag name with the document.
+   *
+   * When a registered element is created, a `readyCallback` method is called
+   * in the scope of the element. The `readyCallback` method can be specified on
+   * either `inOptions.prototype` or `inOptions.lifecycle` with the latter taking
+   * precedence.
+   *
+   * @method register
+   * @param {String} inName The tag name to register. Must include a dash ('-'),
+   *    for example 'x-component'.
+   * @param {Object} inOptions
+   *    @param {String} [inOptions.extends]
+   *      (_off spec_) Tag name of an element to extend (or blank for a new
+   *      element). This parameter is not part of the specification, but instead
+   *      is a hint for the polyfill because the extendee is difficult to infer.
+   *      Remember that the input prototype must chain to the extended element's
+   *      prototype (or HTMLElement.prototype) regardless of the value of
+   *      `extends`.
+   *    @param {Object} inOptions.prototype The prototype to use for the new
+   *      element. The prototype must inherit from HTMLElement.
+   *    @param {Object} [inOptions.lifecycle]
+   *      Callbacks that fire at important phases in the life of the custom
+   *      element.
+   *
+   * @example
+   *      FancyButton = document.register("fancy-button", {
+   *        extends: 'button',
+   *        prototype: Object.create(HTMLButtonElement.prototype, {
+   *          readyCallback: {
+   *            value: function() {
+   *              console.log("a fancy-button was created",
+   *            }
+   *          }
+   *        })
+   *      });
+   * @return {Function} Constructor for the newly registered type.
+   */
+  function register(inName, inOptions) {
+    //console.warn('document.register("' + inName + '", ', inOptions, ')');
+    // construct a defintion out of options
+    // TODO(sjmiles): probably should clone inOptions instead of mutating it
+    var definition = inOptions || {};
+    if (!inName) {
+      // TODO(sjmiles): replace with more appropriate error (EricB can probably
+      // offer guidance)
+      throw new Error('Name argument must not be empty');
+    }
+    // record name
+    definition.name = inName;
+    // must have a prototype, default to an extension of HTMLElement
+    // TODO(sjmiles): probably should throw if no prototype, check spec
+    if (!definition.prototype) {
+      // TODO(sjmiles): replace with more appropriate error (EricB can probably
+      // offer guidance)
+      throw new Error('Options missing required prototype property');
+    }
+    // ensure a lifecycle object so we don't have to null test it
+    definition.lifecycle = definition.lifecycle || {};
+    // build a list of ancestral custom elements (for native base detection)
+    // TODO(sjmiles): we used to need to store this, but current code only
+    // uses it in 'resolveTagName': it should probably be inlined
+    definition.ancestry = ancestry(definition.extends);
+    // extensions of native specializations of HTMLElement require localName
+    // to remain native, and use secondary 'is' specifier for extension type
+    resolveTagName(definition);
+    // some platforms require modifications to the user-supplied prototype
+    // chain
+    resolvePrototypeChain(definition);
+    // overrides to implement attributeChanged callback
+    overrideAttributeApi(definition.prototype);
+    // 7.1.5: Register the DEFINITION with DOCUMENT
+    registerDefinition(inName, definition);
+    // 7.1.7. Run custom element constructor generation algorithm with PROTOTYPE
+    // 7.1.8. Return the output of the previous step.
+    definition.ctor = generateConstructor(definition);
+    definition.ctor.prototype = definition.prototype;
+    // force our .constructor to be our actual constructor
+    definition.prototype.constructor = definition.ctor;
+    // if initial parsing is complete
+    if (scope.ready) {
+      // upgrade any pre-existing nodes of this type
+      scope.upgradeAll(document);
+    }
+    return definition.ctor;
+  }
+
+  function ancestry(inExtends) {
+    var extendee = registry[inExtends];
+    if (extendee) {
+      return ancestry(extendee.extends).concat([extendee]);
+    }
+    return [];
+  }
+
+  function resolveTagName(inDefinition) {
+    // if we are explicitly extending something, that thing is our
+    // baseTag, unless it represents a custom component
+    var baseTag = inDefinition.extends;
+    // if our ancestry includes custom components, we only have a
+    // baseTag if one of them does
+    for (var i=0, a; (a=inDefinition.ancestry[i]); i++) {
+      baseTag = a.is && a.tag;
+    }
+    // our tag is our baseTag, if it exists, and otherwise just our name
+    inDefinition.tag = baseTag || inDefinition.name;
+    if (baseTag) {
+      // if there is a base tag, use secondary 'is' specifier
+      inDefinition.is = inDefinition.name;
+    }
+  }
+
+  function resolvePrototypeChain(inDefinition) {
+    // if we don't support __proto__ we need to locate the native level
+    // prototype for precise mixing in
+    if (!Object.__proto__) {
+      // default prototype
+      var native = HTMLElement.prototype;
+      // work out prototype when using type-extension
+      if (inDefinition.is) {
+        var inst = document.createElement(inDefinition.tag);
+        native = Object.getPrototypeOf(inst);
+      }
+      // ensure __proto__ reference is installed at each point on the prototype
+      // chain.
+      // NOTE: On platforms without __proto__, a mixin strategy is used instead
+      // of prototype swizzling. In this case, this generated __proto__ provides
+      // limited support for prototype traversal.
+      var proto = inDefinition.prototype, ancestor;
+      while (proto && (proto !== native)) {
+        var ancestor = Object.getPrototypeOf(proto);
+        proto.__proto__ = ancestor;
+        proto = ancestor;
+      }
+    }
+    // cache this in case of mixin
+    inDefinition.native = native;
+  }
+
+  // SECTION 4
+
+  function instantiate(inDefinition) {
+    // 4.a.1. Create a new object that implements PROTOTYPE
+    // 4.a.2. Let ELEMENT by this new object
+    //
+    // the custom element instantiation algorithm must also ensure that the
+    // output is a valid DOM element with the proper wrapper in place.
+    //
+    return upgrade(domCreateElement(inDefinition.tag), inDefinition);
+  }
+
+  function upgrade(inElement, inDefinition) {
+    // some definitions specify an 'is' attribute
+    if (inDefinition.is) {
+      inElement.setAttribute('is', inDefinition.is);
+    }
+    // make 'element' implement inDefinition.prototype
+    implement(inElement, inDefinition);
+    // flag as upgraded
+    inElement.__upgraded__ = true;
+    // there should never be a shadow root on inElement at this point
+    // we require child nodes be upgraded before `created`
+    scope.upgradeSubtree(inElement);
+    // lifecycle management
+    created(inElement);
+    // OUTPUT
+    return inElement;
+  }
+
+  function implement(inElement, inDefinition) {
+    // prototype swizzling is best
+    if (Object.__proto__) {
+      inElement.__proto__ = inDefinition.prototype;
+    } else {
+      // where above we can re-acquire inPrototype via
+      // getPrototypeOf(Element), we cannot do so when
+      // we use mixin, so we install a magic reference
+      customMixin(inElement, inDefinition.prototype, inDefinition.native);
+      inElement.__proto__ = inDefinition.prototype;
+    }
+  }
+
+  function customMixin(inTarget, inSrc, inNative) {
+    // TODO(sjmiles): 'used' allows us to only copy the 'youngest' version of
+    // any property. This set should be precalculated. We also need to
+    // consider this for supporting 'super'.
+    var used = {};
+    // start with inSrc
+    var p = inSrc;
+    // sometimes the default is HTMLUnknownElement.prototype instead of
+    // HTMLElement.prototype, so we add a test
+    // the idea is to avoid mixing in native prototypes, so adding
+    // the second test is WLOG
+    while (p !== inNative && p !== HTMLUnknownElement.prototype) {
+      var keys = Object.getOwnPropertyNames(p);
+      for (var i=0, k; k=keys[i]; i++) {
+        if (!used[k]) {
+          Object.defineProperty(inTarget, k,
+              Object.getOwnPropertyDescriptor(p, k));
+          used[k] = 1;
+        }
+      }
+      p = Object.getPrototypeOf(p);
+    }
+  }
+
+  function created(inElement) {
+    // invoke createdCallback
+    if (inElement.createdCallback) {
+      inElement.createdCallback();
+    }
+  }
+
+  // attribute watching
+
+  function overrideAttributeApi(prototype) {
+    // overrides to implement callbacks
+    // TODO(sjmiles): should support access via .attributes NamedNodeMap
+    // TODO(sjmiles): preserves user defined overrides, if any
+    var setAttribute = prototype.setAttribute;
+    prototype.setAttribute = function(name, value) {
+      changeAttribute.call(this, name, value, setAttribute);
+    }
+    var removeAttribute = prototype.removeAttribute;
+    prototype.removeAttribute = function(name, value) {
+      changeAttribute.call(this, name, value, removeAttribute);
+    }
+  }
+
+  function changeAttribute(name, value, operation) {
+    var oldValue = this.getAttribute(name);
+    operation.apply(this, arguments);
+    if (this.attributeChangedCallback
+        && (this.getAttribute(name) !== oldValue)) {
+      this.attributeChangedCallback(name, oldValue);
+    }
+  }
+
+  // element registry (maps tag names to definitions)
+
+  var registry = {};
+
+  function registerDefinition(inName, inDefinition) {
+    if (registry[inName]) {
+      throw new Error('Cannot register a tag more than once');
+    }
+    registry[inName] = inDefinition;
+  }
+
+  function generateConstructor(inDefinition) {
+    return function() {
+      return instantiate(inDefinition);
+    };
+  }
+
+  function createElement(tag, typeExtension) {
+    // TODO(sjmiles): ignore 'tag' when using 'typeExtension', we could
+    // error check it, or perhaps there should only ever be one argument
+    var definition = registry[typeExtension || tag];
+    if (definition) {
+      return new definition.ctor();
+    }
+    return domCreateElement(tag);
+  }
+
+  function upgradeElement(inElement) {
+    if (!inElement.__upgraded__ && (inElement.nodeType === Node.ELEMENT_NODE)) {
+      var type = inElement.getAttribute('is') || inElement.localName;
+      var definition = registry[type];
+      return definition && upgrade(inElement, definition);
+    }
+  }
+
+  function cloneNode(deep) {
+    // call original clone
+    var n = domCloneNode.call(this, deep);
+    // upgrade the element and subtree
+    scope.upgradeAll(n);
+    // return the clone
+    return n;
+  }
+  // capture native createElement before we override it
+
+  var domCreateElement = document.createElement.bind(document);
+
+  // capture native cloneNode before we override it
+
+  var domCloneNode = Node.prototype.cloneNode;
+
+  // exports
+
+  document.register = register;
+  document.createElement = createElement; // override
+  Node.prototype.cloneNode = cloneNode; // override
+
+  scope.registry = registry;
+
+  /**
+   * Upgrade an element to a custom element. Upgrading an element
+   * causes the custom prototype to be applied, an `is` attribute
+   * to be attached (as needed), and invocation of the `readyCallback`.
+   * `upgrade` does nothing if the element is already upgraded, or
+   * if it matches no registered custom tag name.
+   *
+   * @method ugprade
+   * @param {Element} inElement The element to upgrade.
+   * @return {Element} The upgraded element.
+   */
+  scope.upgrade = upgradeElement;
+}
+
+scope.hasNative = hasNative;
+scope.useNative = useNative;
+
+})(window.CustomElements);
+
+(function() {
+
+// import
+
+var IMPORT_LINK_TYPE = window.HTMLImports ? HTMLImports.IMPORT_LINK_TYPE : 'none';
+
+// highlander object for parsing a document tree
+
+var parser = {
+  selectors: [
+    'link[rel=' + IMPORT_LINK_TYPE + ']'
+  ],
+  map: {
+    link: 'parseLink'
+  },
+  parse: function(inDocument) {
+    if (!inDocument.__parsed) {
+      // only parse once
+      inDocument.__parsed = true;
+      // all parsable elements in inDocument (depth-first pre-order traversal)
+      var elts = inDocument.querySelectorAll(parser.selectors);
+      // for each parsable node type, call the mapped parsing method
+      forEach(elts, function(e) {
+        parser[parser.map[e.localName]](e);
+      });
+      // upgrade all upgradeable static elements, anything dynamically
+      // created should be caught by observer
+      CustomElements.upgradeDocument(inDocument);
+      // observe document for dom changes
+      CustomElements.observeDocument(inDocument);
+    }
+  },
+  parseLink: function(linkElt) {
+    // imports
+    if (isDocumentLink(linkElt)) {
+      this.parseImport(linkElt);
+    }
+  },
+  parseImport: function(linkElt) {
+    if (linkElt.content) {
+      parser.parse(linkElt.content);
+    }
+  }
+};
+
+function isDocumentLink(inElt) {
+  return (inElt.localName === 'link'
+      && inElt.getAttribute('rel') === IMPORT_LINK_TYPE);
+}
+
+var forEach = Array.prototype.forEach.call.bind(Array.prototype.forEach);
+
+// exports
+
+CustomElements.parser = parser;
+
+})();
+(function(){
+
+// bootstrap parsing
+
+function bootstrap() {
+  // go async so call stack can unwind
+  setTimeout(function() {
+    // parse document
+    CustomElements.parser.parse(document);
+    // one more pass before register is 'live'
+    CustomElements.upgradeDocument(document);
+    // set internal 'ready' flag, now document.register will trigger
+    // synchronous upgrades
+    CustomElements.ready = true;
+    // capture blunt profiling data
+    CustomElements.readyTime = Date.now();
+    if (window.HTMLImports) {
+      CustomElements.elapsed = CustomElements.readyTime - HTMLImports.readyTime;
+    }
+    // notify the system that we are bootstrapped
+    document.body.dispatchEvent(
+      new CustomEvent('WebComponentsReady', {bubbles: true})
+    );
+  }, 0);
+}
+
+// CustomEvent shim for IE
+if (typeof window.CustomEvent !== 'function') {
+  window.CustomEvent = function(inType) {
+     var e = document.createEvent('HTMLEvents');
+     e.initEvent(inType, true, true);
+     return e;
+  };
+}
+
+if (document.readyState === 'complete') {
+  bootstrap();
+} else {
+  var loadEvent = window.HTMLImports ? 'HTMLImportsLoaded' : 'DOMContentLoaded';
+  window.addEventListener(loadEvent, bootstrap);
+}
+
+})();