diff --git a/externs/closure-types.js b/externs/closure-types.js
index 118f0085c6..46ecd93183 100644
--- a/externs/closure-types.js
+++ b/externs/closure-types.js
@@ -529,7 +529,7 @@ Polymer_LegacyElementMixin.prototype.instanceTemplate = function(template){};
 /**
 * @param {string} type
 * @param {*=} detail
-* @param {Object=} options
+* @param {fireOptions=} options
 * @return {Event}
 */
 Polymer_LegacyElementMixin.prototype.fire = function(type, detail, options){};
@@ -547,7 +547,7 @@ Polymer_LegacyElementMixin.prototype.listen = function(node, eventName, methodNa
 Polymer_LegacyElementMixin.prototype.unlisten = function(node, eventName, methodName){};
 /**
 * @param {string=} direction
-* @param {HTMLElement=} node
+* @param {Element=} node
 */
 Polymer_LegacyElementMixin.prototype.setScrollDirection = function(direction, node){};
 /**
@@ -601,7 +601,7 @@ Polymer_LegacyElementMixin.prototype.getContentChildren = function(slctr){};
 */
 Polymer_LegacyElementMixin.prototype.isLightDescendant = function(node){};
 /**
-* @param {HTMLElement=} node
+* @param {Element=} node
 * @return {boolean}
 */
 Polymer_LegacyElementMixin.prototype.isLocalDescendant = function(node){};
@@ -668,25 +668,25 @@ Polymer_LegacyElementMixin.prototype.elementMatches = function(selector, node){}
 /**
 * @param {string} name
 * @param {boolean=} bool
-* @param {HTMLElement=} node
+* @param {Element=} node
 */
 Polymer_LegacyElementMixin.prototype.toggleAttribute = function(name, bool, node){};
 /**
 * @param {string} name
 * @param {boolean=} bool
-* @param {HTMLElement=} node
+* @param {Element=} node
 */
 Polymer_LegacyElementMixin.prototype.toggleClass = function(name, bool, node){};
 /**
 * @param {string} transformText
-* @param {HTMLElement=} node
+* @param {Element=} node
 */
 Polymer_LegacyElementMixin.prototype.transform = function(transformText, node){};
 /**
 * @param {number} x
 * @param {number} y
 * @param {number} z
-* @param {HTMLElement=} node
+* @param {Element=} node
 */
 Polymer_LegacyElementMixin.prototype.translate3d = function(x, y, z, node){};
 /**
@@ -713,10 +713,11 @@ Polymer_LegacyElementMixin.prototype._warn = function(args){};
 */
 Polymer_LegacyElementMixin.prototype._error = function(args){};
 /**
+* @param {string} methodName
 * @param {*} args
-* @return {string}
+* @return {Array}
 */
-Polymer_LegacyElementMixin.prototype._logf = function(args){};
+Polymer_LegacyElementMixin.prototype._logf = function(methodName, args){};
 /**
 * @record
 */
diff --git a/lib/legacy/legacy-element-mixin.html b/lib/legacy/legacy-element-mixin.html
index 4e0b5cfec3..fa1e699267 100644
--- a/lib/legacy/legacy-element-mixin.html
+++ b/lib/legacy/legacy-element-mixin.html
@@ -38,7 +38,7 @@
    * @memberof Polymer
    * @summary Element class mixin that provides Polymer's "legacy" API
    */
-  Polymer.LegacyElementMixin = Polymer.dedupingMixin(base => {
+  Polymer.LegacyElementMixin = Polymer.dedupingMixin((base) => {
 
     /**
      * @constructor
@@ -59,6 +59,15 @@
       'all': 'auto'
     };
 
+    /**
+     * @typedef {{
+     *   bubbles: (boolean|undefined),
+     *   cancelable: (boolean|undefined),
+     *   composed: (boolean|undefined)
+     * }}
+     */
+    let fireOptions; // eslint-disable-line no-unused-vars
+
     /**
      * @polymerMixinClass
      * @implements {Polymer_LegacyElementMixin}
@@ -257,7 +266,7 @@
        * @param {Element} node Element to set attribute to.
        */
       serializeValueToAttribute(value, attribute, node) {
-        this._valueToNodeAttribute(node || this, value, attribute);
+        this._valueToNodeAttribute(/** @type {Element} */ (node || this), value, attribute);
       }
 
       /**
@@ -337,13 +346,15 @@
 
       /* **** Begin Events **** */
 
+
+
       /**
        * Dispatches a custom event with an optional detail value.
        *
        * @param {string} type Name of event type.
        * @param {*=} detail Detail value containing event-specific
        *   payload.
-       * @param {Object=} options Object specifying options.  These may include:
+       * @param {fireOptions=} options Object specifying options.  These may include:
        *  `bubbles` (boolean, defaults to `true`),
        *  `cancelable` (boolean, defaults to false), and
        *  `node` on which to fire the event (HTMLElement, defaults to `this`).
@@ -372,7 +383,7 @@
        * @param {string} methodName Name of handler method on `this` to call.
        */
       listen(node, eventName, methodName) {
-        node = node || this;
+        node = /** @type {Element} */ (node || this);
         let hbl = this.__boundListeners ||
           (this.__boundListeners = new WeakMap());
         let bl = hbl.get(node);
@@ -397,7 +408,7 @@
        anymore.
        */
       unlisten(node, eventName, methodName) {
-        node = node || this;
+        node = /** @type {Element} */ (node || this);
         let bl = this.__boundListeners && this.__boundListeners.get(node);
         let key = eventName + methodName;
         let handler = bl && bl[key];
@@ -418,11 +429,11 @@
        *
        * @param {string=} direction Direction to allow scrolling
        * Defaults to `all`.
-       * @param {HTMLElement=} node Element to apply scroll direction setting.
+       * @param {Element=} node Element to apply scroll direction setting.
        * Defaults to `this`.
        */
       setScrollDirection(direction, node) {
-        Polymer.Gestures.setTouchAction(node || this, DIRECTION_MAP[direction] || 'auto');
+        Polymer.Gestures.setTouchAction(/** @type {Element} */ (node || this), DIRECTION_MAP[direction] || 'auto');
       }
       /* **** End Events **** */
 
@@ -442,6 +453,7 @@
        * Return the element whose local dom within which this element
        * is contained. This is a shorthand for
        * `this.getRootNode().host`.
+       * @this {Element}
        */
       get domHost() {
         let root = this.getRootNode();
@@ -467,11 +479,11 @@
        * childNodes list is the same as the element's childNodes except that
        * any `<content>` elements are replaced with the list of nodes distributed
        * to the `<content>`, the result of its `getDistributedNodes` method.
-       *
+       * @this {Element}
        * @return {Array<Node>} List of effctive child nodes.
        */
       getEffectiveChildNodes() {
-        return Polymer.dom(this).getEffectiveChildNodes();
+        return /** @type {Polymer.DomApi} */ (Polymer.dom(this)).getEffectiveChildNodes();
       }
 
       /**
@@ -479,10 +491,11 @@
        * `selector`. These can be dom children or elements distributed to
        * children that are insertion points.
        * @param {string} selector Selector to run.
+       * @this {Element}
        * @return {Array<Node>} List of distributed elements that match selector.
        */
       queryDistributedElements(selector) {
-        return Polymer.dom(this).queryDistributedElements(selector);
+        return /** @type {Polymer.DomApi} */ (Polymer.dom(this)).queryDistributedElements(selector);
       }
 
       /**
@@ -495,7 +508,7 @@
        */
       getEffectiveChildren() {
         let list = this.getEffectiveChildNodes();
-        return list.filter(function(n) {
+        return list.filter(function(/** @type {Node} */ n) {
           return (n.nodeType === Node.ELEMENT_NODE);
         });
       }
@@ -553,7 +566,7 @@
        */
       getContentChildNodes(slctr) {
         let content = this.root.querySelector(slctr || 'slot');
-        return content ? Polymer.dom(content).getDistributedNodes() : [];
+        return content ? /** @type {Polymer.DomApi} */(Polymer.dom(content)).getDistributedNodes() : [];
       }
 
       /**
@@ -580,6 +593,7 @@
        * Checks whether an element is in this element's light DOM tree.
        *
        * @param {?Node} node The element to be checked.
+       * @this {Element}
        * @return {boolean} true if node is in this element's light DOM tree.
        */
       isLightDescendant(node) {
@@ -590,7 +604,7 @@
       /**
        * Checks whether an element is in this element's local DOM tree.
        *
-       * @param {HTMLElement=} node The element to be checked.
+       * @param {Element=} node The element to be checked.
        * @return {boolean} true if node is in this element's local DOM tree.
        */
       isLocalDescendant(node) {
@@ -767,7 +781,7 @@
        * @return {boolean} Whether the element matches the selector.
        */
       elementMatches(selector, node) {
-        return Polymer.dom.matchesSelector(node || this, selector);
+        return Polymer.dom.matchesSelector(/** @type {!Element} */ (node || this), selector);
       }
 
       /**
@@ -776,10 +790,10 @@
        * @param {string} name HTML attribute name
        * @param {boolean=} bool Boolean to force the attribute on or off.
        *    When unspecified, the state of the attribute will be reversed.
-       * @param {HTMLElement=} node Node to target.  Defaults to `this`.
+       * @param {Element=} node Node to target.  Defaults to `this`.
        */
       toggleAttribute(name, bool, node) {
-        node = node || this;
+        node = /** @type {Element} */ (node || this);
         if (arguments.length == 1) {
           bool = !node.hasAttribute(name);
         }
@@ -797,10 +811,10 @@
        * @param {string} name CSS class name
        * @param {boolean=} bool Boolean to force the class on or off.
        *    When unspecified, the state of the class will be reversed.
-       * @param {HTMLElement=} node Node to target.  Defaults to `this`.
+       * @param {Element=} node Node to target.  Defaults to `this`.
        */
       toggleClass(name, bool, node) {
-        node = node || this;
+        node = /** @type {Element} */ (node || this);
         if (arguments.length == 1) {
           bool = !node.classList.contains(name);
         }
@@ -815,11 +829,11 @@
        * Cross-platform helper for setting an element's CSS `transform` property.
        *
        * @param {string} transformText Transform setting.
-       * @param {HTMLElement=} node Element to apply the transform to.
+       * @param {Element=} node Element to apply the transform to.
        * Defaults to `this`
        */
       transform(transformText, node) {
-        node = node || this;
+        node = /** @type {Element} */ (node || this);
         node.style.webkitTransform = transformText;
         node.style.transform = transformText;
       }
@@ -831,11 +845,11 @@
        * @param {number} x X offset.
        * @param {number} y Y offset.
        * @param {number} z Z offset.
-       * @param {HTMLElement=} node Element to apply the transform to.
+       * @param {Element=} node Element to apply the transform to.
        * Defaults to `this`.
        */
       translate3d(x, y, z, node) {
-        node = node || this;
+        node = /** @type {Element} */ (node || this);
         this.transform('translate3d(' + x + ',' + y + ',' + z + ')', node);
       }
 
@@ -895,7 +909,7 @@
       /**
        * Facades `console.log` as an override point.
        *
-       * @param {...*} var_args Array of strings or objects to log
+       * @param {...*} args Array of strings or objects to log
        */
       _log(...args) {
         this._logger('log', args);
@@ -904,7 +918,7 @@
       /**
        * Facades `console.warn` as an override point.
        *
-       * @param {...*} var_args Array of strings or objects to log
+       * @param {...*} args Array of strings or objects to log
        */
       _warn(...args) {
         this._logger('warn', args);
@@ -913,7 +927,7 @@
       /**
        * Facades `console.error` as an override point.
        *
-       * @param {...*} var_args Array of strings or objects to log
+       * @param {...*} args Array of strings or objects to log
        */
       _error(...args) {
         this._logger('error', args)
@@ -923,16 +937,18 @@
        * Formats a message using the element type an a method name.
        *
        * @param {string} methodName Method name to associate with message
-       * @param {...*} var_args Array of strings or objects to log
-       * @return {string} String with formatting information for `console`
+       * @param {...*} args Array of strings or objects to log
+       * @return {Array} Array with formatting information for `console`
        *   logging.
        */
-      _logf(...args) {
-        return ['[%s::%s]', this.is, ...args];
+      _logf(methodName, ...args) {
+        return ['[%s::%s]', this.is, methodName, ...args];
       }
 
     }
 
+    LegacyElement.prototype.is = '';
+
     return LegacyElement;
 
   });
diff --git a/lib/legacy/polymer.dom.html b/lib/legacy/polymer.dom.html
index 0d7f62dc8d..2e9739da3f 100644
--- a/lib/legacy/polymer.dom.html
+++ b/lib/legacy/polymer.dom.html
@@ -287,6 +287,8 @@
     }
   }
 
+  Polymer.DomApi = DomApi;
+
   /**
    * Legacy DOM and Event manipulation API wrapper factory used to abstract
    * differences between native Shadow DOM and "Shady DOM" when polyfilling on
diff --git a/lib/utils/async.html b/lib/utils/async.html
index 19293ddc1f..0465531b31 100644
--- a/lib/utils/async.html
+++ b/lib/utils/async.html
@@ -173,7 +173,7 @@
        *
        * @memberof Polymer.Async.timeOut
        * @param {Function} callback Callback to run
-       * @return {*} Handle used for canceling task
+       * @return {number} Handle used for canceling task
        */
       run(callback) {
         microtaskNode.textContent = microtaskNodeContent++;