Update externs from internal

externs/polymer-externs.js

@@ -47,6 +47,8 @@ PolymerInit.prototype.template;
 PolymerInit.prototype.hostAttributes;
 /** @type {(!Object<string, string> | undefined)} */
 PolymerInit.prototype.listeners;
+/** @type {(!Object| !Array<!Object> | undefined)} */
+PolymerInit.prototype.behaviors;
 
 /** @record */
 let PolymerElementConstructor = function () {};
@@ -110,6 +112,8 @@ function JSCompiler_renameProperty(string, obj) {}
 function PolymerTelemetry() {}
 /** @type {number} */
 PolymerTelemetry.instanceCount;
+/** @type {function():void} */
+PolymerTelemetry.incrementInstanceCount;
 /** @type {Array<HTMLElement>} */
 PolymerTelemetry.registrations;
 /** @type {function(HTMLElement)} */
@@ -125,6 +129,12 @@ Polymer.telemetry;
 /** @type {string} */
 Polymer.version;
 
+/** @type {boolean} */
+Polymer.legacyOptimizations;
+
+/** @type {boolean} */
+Polymer.syncInitialRender;
+
 // nb. This is explicitly 'var', as Closure Compiler checks that this is the case.
 /**
  * @constructor

externs/webcomponents-externs.js

@@ -18,8 +18,8 @@ var HTMLImports = {
    */
   whenReady(callback) {},
   /**
-   * @param {Element} element
-   * @returns {Document} document
+   * @param {!Node} element
+   * @return {?HTMLLinkElement|?Document|undefined}
    */
   importForElement(element) {}
 };
@@ -42,7 +42,11 @@ var ShadyDOM = {
   /**
    * @param {Node} node
    */
-  patch(node) {}
+  patch(node) {},
+  /**
+   * @param {!ShadowRoot} shadowroot
+   */
+  flushInitial(shadowroot) {}
 };
 
 window.ShadyDOM = ShadyDOM;