diff --git a/externs/iterator.js b/externs/iterator.js
new file mode 100644
index 0000000000..11d16c3011
--- /dev/null
+++ b/externs/iterator.js
@@ -0,0 +1,34 @@
+/**
+ * Copyright 2015 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * @fileoverview Iterator externs missing from closure.
+ * @externs
+ */
+
+
+
+/**
+ * @interface
+ * @template VALUE
+ * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/The_Iterator_protocol
+ */
+function Iterator() {}
+
+
+/**
+ * @return {{value:VALUE, done:boolean}}
+ */
+Iterator.prototype.next = function() {};
+
diff --git a/externs/mediakeys.js b/externs/mediakeys.js
index 120f05b260..21f4c4597a 100644
--- a/externs/mediakeys.js
+++ b/externs/mediakeys.js
@@ -23,10 +23,6 @@
 var BufferSource;
 
 
-/** @typedef {!Object.<BufferSource, string>} */
-var MediaKeyStatuses;
-
-
 /**
  * @param {string} keySystem
  * @param {Array.<Object>=} opt_supportedConfigurations
@@ -43,14 +39,6 @@ Navigator.prototype.requestMediaKeySystemAccess =
 HTMLMediaElement.prototype.mediaKeys;
 
 
-/**
- * NOTE: Not yet implemented as of Chrome 40.  Type may be incorrect.
- * @type {string}
- * @const
- */
-HTMLMediaElement.prototype.waitingFor;
-
-
 /**
  * @param {MediaKeys} mediaKeys
  * @return {!Promise}
@@ -68,7 +56,6 @@ MediaKeySystemAccess.prototype.createMediaKeys = function() {};
 
 
 /**
- * NOTE: Not yet implemented as of Chrome 40.  Type may be incorrect.
  * @return {Object}
  */
 MediaKeySystemAccess.prototype.getConfiguration = function() {};
@@ -99,6 +86,60 @@ MediaKeys.prototype.setServerCertificate = function(serverCertificate) {};
 
 
 
+/**
+ * @interface
+ */
+function MediaKeyStatusMap() {}
+
+
+/**
+ * @type {number}
+ * @const
+ */
+MediaKeyStatusMap.prototype.size;
+
+
+/**
+ * Array entry 0 is the key, 1 is the value.
+ * @return {Iterator.<Array.<!BufferSource|string>>}
+ */
+MediaKeyStatusMap.prototype.entries = function() {};
+
+
+/**
+ * The functor is called with each value.
+ * @param {function(string)} fn
+ */
+MediaKeyStatusMap.prototype.forEach = function(fn) {};
+
+
+/**
+ * @param {!BufferSource} keyId
+ * @return {string|undefined}
+ */
+MediaKeyStatusMap.prototype.get = function(keyId) {};
+
+
+/**
+ * @param {!BufferSource} keyId
+ * @return {boolean}
+ */
+MediaKeyStatusMap.prototype.has = function(keyId) {};
+
+
+/**
+ * @return {Iterator.<!BufferSource>}
+ */
+MediaKeyStatusMap.prototype.keys = function() {};
+
+
+/**
+ * @return {Iterator.<string>}
+ */
+MediaKeyStatusMap.prototype.values = function() {};
+
+
+
 /**
  * @interface
  * @extends {EventTarget}
@@ -128,8 +169,7 @@ MediaKeySession.prototype.closed;
 
 
 /**
- * NOTE: Not yet implemented as of Chrome 40.  Type may be incorrect.
- * @type {!MediaKeyStatuses}
+ * @type {!MediaKeyStatusMap}
  * @const
  */
 MediaKeySession.prototype.keyStatuses;
diff --git a/lib/player/player.js b/lib/player/player.js
index 86469e5557..b9fb2675bc 100644
--- a/lib/player/player.js
+++ b/lib/player/player.js
@@ -40,6 +40,10 @@ goog.require('shaka.util.Uint8ArrayUtils');
  * @property {string} type 'error'
  * @property {boolean} bubbles true
  * @property {!Error} detail An object which contains details on the error.
+ *    The error's 'type' property will help you identify the specific error
+ *    condition and display an appropriate message or error indicator to the
+ *    user.  The error's 'message' property contains English text which can
+ *    be useful during debugging.
  * @export
  */
 
@@ -406,6 +410,7 @@ shaka.player.Player.prototype.generateFakeEncryptedEvents_ =
  * @private
  */
 shaka.player.Player.prototype.setVideoEventListeners_ = function() {
+  this.eventManager_.listen(this.video_, 'error', this.onError_.bind(this));
   // TODO(story 1891509): Connect these events to the UI.
   this.eventManager_.listen(this.video_, 'play', this.onPlay_.bind(this));
   this.eventManager_.listen(this.video_, 'playing', this.onPlaying_.bind(this));
@@ -443,9 +448,12 @@ shaka.player.Player.prototype.onEncrypted_ = function(event) {
   var session = this.mediaKeys_.createSession();
   this.sessions_.push(session);
 
-  this.eventManager_.listen(
-      session, 'message', /** @type {shaka.util.EventManager.ListenerType} */(
+  this.eventManager_.listen(session, 'message',
+      /** @type {shaka.util.EventManager.ListenerType} */(
           this.onSessionMessage_.bind(this)));
+  this.eventManager_.listen(session, 'keystatuseschange',
+      /** @type {shaka.util.EventManager.ListenerType} */(
+          this.onKeyStatusChange_.bind(this)));
 
   var p = session.generateRequest(event.initDataType, event.initData);
   this.requestGenerated_[initDataKey] = true;
@@ -476,6 +484,29 @@ shaka.player.Player.prototype.onSessionMessage_ = function(event) {
 };
 
 
+/**
+ * EME status-change handler.
+ *
+ * @param {!Event} event
+ * @private
+ */
+shaka.player.Player.prototype.onKeyStatusChange_ = function(event) {
+  shaka.log.info('onKeyStatusChange_', event);
+  var session = /** @type {!MediaKeySession} */(event.target);
+  var map = session.keyStatuses;
+  var i = map.values();
+  for (var v = i.next(); !v.done; v = i.next()) {
+    var message = shaka.player.Player.KEY_STATUS_ERROR_MAP_[v.value];
+    if (message) {
+      var error = new Error(message);
+      error.type = v.value;
+      var event = shaka.util.FakeEvent.createErrorEvent(error);
+      this.dispatchEvent(event);
+    }
+  }
+};
+
+
 /**
  * Requests a license.
  *
@@ -538,6 +569,31 @@ shaka.player.Player.prototype.onFirstTimestamp_ = function(event) {
 };
 
 
+/**
+ * Video error event handler.
+ *
+ * @param {!Event} event
+ * @private
+ */
+shaka.player.Player.prototype.onError_ = function(event) {
+  var code = this.video_.error.code;
+  if (code == MediaError['MEDIA_ERR_ABORTED']) {
+    // Ignore this error code, which should only occur when navigating away or
+    // deliberately stopping playback of HTTP content.
+    return;
+  }
+
+  shaka.log.debug('onError_', event, code);
+  var message = shaka.player.Player.MEDIA_ERROR_MAP_[code] ||
+                'Unknown playback error.';
+
+  var error = new Error(message);
+  error.type = 'playback';
+  var event = shaka.util.FakeEvent.createErrorEvent(error);
+  this.dispatchEvent(event);
+};
+
+
 /**
  * Video play event handler.
  *
@@ -978,3 +1034,40 @@ shaka.player.Player.prototype.onWatchdogTimer_ = function() {
  */
 shaka.player.Player.UNDERFLOW_THRESHOLD_ = 0.050;
 
+
+/**
+ * A map of key statuses to errors.  Not every key status appears in the map,
+ * in which case that key status is not treated as an error.
+ *
+ * @private {!Object.<string, string>}
+ * @const
+ */
+shaka.player.Player.KEY_STATUS_ERROR_MAP_ = {
+  'output-not-allowed': 'The required output protection is not available.',
+  'expired': 'A required key has expired and the content cannot be decrypted.',
+  'internal-error': 'An unknown error has occurred in the CDM.'
+};
+
+
+/**
+ * A map of MediaError codes to error messages.  The JS interpreter won't take
+ * a symbolic name as a key, so the symbolic names for these error codes appear
+ * in comments after the number.
+ *
+ * @private {!Object.<number, string>}
+ * @const
+ */
+shaka.player.Player.MEDIA_ERROR_MAP_ = {
+  // This should not occur for DASH sources, but may occur for HTTP sources.
+  2: // MediaError.MEDIA_ERR_NETWORK
+      'A network failure occured while loading media content.',
+
+  3: // MediaError.MEDIA_ERR_DECODE
+      'The browser failed to decode the media content.',
+
+  // This is also unlikely for DASH sources, but HTTP sources do not check
+  // browser support before beginning playback.
+  4: // MediaError.MEDIA_ERR_SRC_NOT_SUPPORTED
+      'The browser does not support the media content.'
+};
+
diff --git a/lib/polyfill/patchedmediakeys_v01b.js b/lib/polyfill/patchedmediakeys_v01b.js
index 5a5cadbb7b..6dcdc5964f 100644
--- a/lib/polyfill/patchedmediakeys_v01b.js
+++ b/lib/polyfill/patchedmediakeys_v01b.js
@@ -476,9 +476,9 @@ shaka.polyfill.PatchedMediaKeys.v01b.MediaKeySession =
   /** @type {!shaka.util.PublicPromise} */
   this.closed = new shaka.util.PublicPromise();
 
-  /** @type {!MediaKeyStatuses} */
-  this.keyStatuses = {};
-  // TODO: key status and 'keyschange' events unsupported
+  /** @type {!MediaKeyStatusMap} */
+  this.keyStatuses =
+      new shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap();
 };
 goog.inherits(shaka.polyfill.PatchedMediaKeys.v01b.MediaKeySession,
               shaka.util.FakeEventTarget);
@@ -516,7 +516,7 @@ shaka.polyfill.PatchedMediaKeys.v01b.MediaKeySession.prototype.ready =
   // internally, that the session is no longer new.  This allows us to set
   // the messageType attribute of 'message' events.
   this.expiration = Number.POSITIVE_INFINITY;
-  // TODO: key status and 'keyschange' events unsupported
+  this.updateKeyStatus_('usable');
 
   if (this.updatePromise_) {
     this.updatePromise_.resolve();
@@ -551,6 +551,17 @@ shaka.polyfill.PatchedMediaKeys.v01b.MediaKeySession.prototype.handleError =
     error.method = 'update';
     this.updatePromise_.reject(error);
     this.updatePromise_ = null;
+  } else {
+    // This mapping of key statuses is imperfect at best.
+    var code = event.errorCode.code;
+    var systemCode = event.systemCode;
+    if (code == MediaKeyError['MEDIA_KEYERR_OUTPUT']) {
+      this.updateKeyStatus_('output-not-allowed');
+    } else if (systemCode == 1) {
+      this.updateKeyStatus_('expired');
+    } else {
+      this.updateKeyStatus_('internal-error');
+    }
   }
 };
 
@@ -677,6 +688,20 @@ shaka.polyfill.PatchedMediaKeys.v01b.MediaKeySession.prototype.update_ =
 };
 
 
+/**
+ * Update key status and dispatch a 'keystatuseschange' event.
+ *
+ * @param {string} status
+ * @private
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeySession.prototype.
+    updateKeyStatus_ = function(status) {
+  this.keyStatuses.setStatus(status);
+  var event = shaka.util.FakeEvent.create({type: 'keystatuseschange'});
+  this.dispatchEvent(event);
+};
+
+
 /** @override */
 shaka.polyfill.PatchedMediaKeys.v01b.MediaKeySession.prototype.generateRequest =
     function(initDataType, initData) {
@@ -750,3 +775,161 @@ shaka.polyfill.PatchedMediaKeys.v01b.MediaKeySession.prototype.remove =
   return this.close();
 };
 
+
+
+/**
+ * An implementation of Iterator.
+ *
+ * @param {!Array.<VALUE>} values
+ *
+ * @constructor
+ * @implements {Iterator}
+ * @template VALUE
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.Iterator = function(values) {
+  /** @private {!Array.<VALUE>} */
+  this.values_ = values;
+
+  /** @private {number} */
+  this.index_ = 0;
+};
+
+
+/**
+ * @return {{value:VALUE, done:boolean}}
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.Iterator.prototype.next = function() {
+  if (this.index_ >= this.values_.length) {
+    return {value: undefined, done: true};
+  }
+  return {value: this.values_[this.index_++], done: false};
+};
+
+
+
+/**
+ * An implementation of MediaKeyStatusMap.
+ * This fakes a map with a single key ID.
+ *
+ * @constructor
+ * @implements {MediaKeyStatusMap}
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap = function() {
+  /**
+   * @type {number}
+   */
+  this.size = 0;
+
+  /**
+   * @private {string|undefined}
+   */
+  this.status_ = undefined;
+};
+
+
+/**
+ * @const {!Uint8Array}
+ * @private
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.KEY_ID_ =
+    shaka.util.Uint8ArrayUtils.fromString('FAKE_KEY_ID');
+
+
+/**
+ * An internal method used by the session to set key status.
+ * @param {string|undefined} status
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.prototype.setStatus =
+    function(status) {
+  this.size = status == undefined ? 0 : 1;
+  this.status_ = status;
+};
+
+
+/**
+ * Array entry 0 is the key, 1 is the value.
+ * @return {Iterator.<Array.<!BufferSource|string>>}
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.prototype.entries =
+    function() {
+  var fakeKeyId =
+      shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.KEY_ID_;
+  /** @type {!Array.<!Array.<!BufferSource|string>>} */
+  var arr = [];
+  if (this.status_) {
+    arr.push([fakeKeyId, this.status_]);
+  }
+  return new shaka.polyfill.PatchedMediaKeys.v01b.Iterator(arr);
+};
+
+
+/**
+ * The functor is called with each value.
+ * @param {function(string)} fn
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.prototype.forEach =
+    function(fn) {
+  if (this.status_) {
+    fn(this.status_);
+  }
+};
+
+
+/**
+ * @param {!BufferSource} keyId
+ * @return {string|undefined}
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.prototype.get =
+    function(keyId) {
+  if (this.has(keyId)) {
+    return this.status_;
+  }
+  return undefined;
+};
+
+
+/**
+ * @param {!BufferSource} keyId
+ * @return {boolean}
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.prototype.has =
+    function(keyId) {
+  var fakeKeyId =
+      shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.KEY_ID_;
+  if (this.status_ &&
+      shaka.util.Uint8ArrayUtils.equal(new Uint8Array(keyId), fakeKeyId)) {
+    return true;
+  }
+  return false;
+};
+
+
+/**
+ * @return {Iterator.<!BufferSource>}
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.prototype.keys =
+    function() {
+  var fakeKeyId =
+      shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.KEY_ID_;
+  /** @type {!Array.<!BufferSource>} */
+  var arr = [];
+  if (this.status_) {
+    arr.push(fakeKeyId);
+  }
+  return new shaka.polyfill.PatchedMediaKeys.v01b.Iterator(arr);
+};
+
+
+/**
+ * @return {Iterator.<string>}
+ */
+shaka.polyfill.PatchedMediaKeys.v01b.MediaKeyStatusMap.prototype.values =
+    function() {
+  /** @type {!Array.<string>} */
+  var arr = [];
+  if (this.status_) {
+    arr.push(this.status_);
+  }
+  return new shaka.polyfill.PatchedMediaKeys.v01b.Iterator(arr);
+};
+