Fix type info and initData types in EME polyfills

The latest Closure Compiler initially complained about "initData" not
being a known property of "Event".  Correcting the type to
MediaEncryptedEvent exposed a potential bug, which is that we were
assigning Uint8Array in some cases instead of the correct ArrayBuffer.
This fixes both the type of the event and converts the Uint8Arrays to
ArrayBuffers.

This also works around a complaint about "code" on "Error".  We use
"Error" objects as look-alikes for DOMException because there is no
exposed constructor for DOMExceptions.  To satisfy the compiler, we
use square brackets now to set the "code" field on these DOMException
look-alikes.

Finally, this removes the "method" field on certain Errors in the
WebKit EME polyfill.  These must have been leftover from some
debugging, and are not used at all.

Issue shaka-project#2528

Change-Id: I32c4617b14a30c412d5bc532ec17a46fdc1fea1a

lib/polyfill/patchedmediakeys_apple.js

@@ -136,6 +136,8 @@ shaka.polyfill.PatchedMediaKeysApple = class {
    *
    * @this {!HTMLMediaElement}
    * @param {!MediaKeyEvent} event
+   * @suppress {constantProperty} We reassign what would be const on a real
+   *   MediaEncryptedEvent, but in our look-alike event.
    * @private
    */
   static onWebkitNeedKey_(event) {
@@ -168,8 +170,11 @@ shaka.polyfill.PatchedMediaKeysApple = class {
     // NOTE: Because "this" is a real EventTarget, the event we dispatch here
     // must also be a real Event.
     const event2 = new Event('encrypted');
-    event2.initDataType = 'skd';
-    event2.initData = shaka.util.BufferUtils.toArrayBuffer(initData);
+
+    const encryptedEvent =
+      /** @type {!MediaEncryptedEvent} */(/** @type {?} */(event2));
+    encryptedEvent.initDataType = 'skd';
+    encryptedEvent.initData = shaka.util.BufferUtils.toArrayBuffer(initData);
 
     this.dispatchEvent(event2);
   }
@@ -209,11 +214,11 @@ shaka.polyfill.PatchedMediaKeysApple.MediaKeySystemAccess = class {
       }
     }
 
-    // As per the spec, this should be a DOMException, but there is not a
-    // public constructor for DOMException.
+    // According to the spec, this should be a DOMException, but there is not a
+    // public constructor for that.  So we make this look-alike instead.
     const unsupportedKeySystemError = new Error('Unsupported keySystem');
     unsupportedKeySystemError.name = 'NotSupportedError';
-    unsupportedKeySystemError.code = DOMException.NOT_SUPPORTED_ERR;
+    unsupportedKeySystemError['code'] = DOMException.NOT_SUPPORTED_ERR;
     throw unsupportedKeySystemError;
   }
 
@@ -597,7 +602,7 @@ class extends shaka.util.FakeEventTarget {
     shaka.log.debug('PatchedMediaKeysApple.onWebkitKeyError_', event);
 
     const error = new Error('EME PatchedMediaKeysApple key error');
-    error.errorCode = this.nativeMediaKeySession_.error;
+    error['errorCode'] = this.nativeMediaKeySession_.error;
 
     if (this.generateRequestPromise_ != null) {
       this.generateRequestPromise_.reject(error);

lib/polyfill/patchedmediakeys_ms.js

@@ -86,6 +86,8 @@ shaka.polyfill.PatchedMediaKeysMs = class {
    *
    * @this {!HTMLMediaElement}
    * @param {!MediaKeyEvent} event
+   * @suppress {constantProperty} We reassign what would be const on a real
+   *   MediaEncryptedEvent, but in our look-alike event.
    * @private
    */
   static onMsNeedKey_(event) {
@@ -97,10 +99,14 @@ shaka.polyfill.PatchedMediaKeysMs = class {
     // NOTE: Because "this" is a real EventTarget, on IE, the event we dispatch
     // here must also be a real Event.
     const event2 =
-    /** @type {!CustomEvent} */ (document.createEvent('CustomEvent'));
+      /** @type {!CustomEvent} */(document.createEvent('CustomEvent'));
     event2.initCustomEvent('encrypted', false, false, null);
-    event2.initDataType = 'cenc';
-    event2.initData = shaka.util.Pssh.normaliseInitData(event.initData);
+
+    const encryptedEvent =
+      /** @type {!MediaEncryptedEvent} */(/** @type {?} */(event2));
+    encryptedEvent.initDataType = 'cenc';
+    encryptedEvent.initData = shaka.util.BufferUtils.toArrayBuffer(
+        shaka.util.Pssh.normaliseInitData(event.initData));
 
     this.dispatchEvent(event2);
   }
@@ -196,11 +202,11 @@ shaka.polyfill.PatchedMediaKeysMs.MediaKeySystemAccess = class {
       }
     }  // for each cfg in supportedConfigurations
 
-    // As per the spec, this should be a DOMException, but there is not a
-    // public constructor for this.
+    // According to the spec, this should be a DOMException, but there is not a
+    // public constructor for that.  So we make this look-alike instead.
     const unsupportedKeySystemError = new Error('Unsupported keySystem');
     unsupportedKeySystemError.name = 'NotSupportedError';
-    unsupportedKeySystemError.code = DOMException.NOT_SUPPORTED_ERR;
+    unsupportedKeySystemError['code'] = DOMException.NOT_SUPPORTED_ERR;
     throw unsupportedKeySystemError;
   }
 
@@ -566,7 +572,7 @@ class extends shaka.util.FakeEventTarget {
     shaka.log.debug('PatchedMediaKeysMs.onMsKeyError_', event);
 
     const error = new Error('EME PatchedMediaKeysMs key error');
-    error.errorCode = this.nativeMediaKeySession_.error;
+    error['errorCode'] = this.nativeMediaKeySession_.error;
 
     if (this.generateRequestPromise_ != null) {
       this.generateRequestPromise_.reject(error);

lib/polyfill/patchedmediakeys_webkit.js

@@ -283,9 +283,12 @@ shaka.polyfill.PatchedMediaKeysWebkit.MediaKeySystemAccess = class {
     if (keySystem == 'org.w3.clearkey' || keySystem == 'com.widevine.alpha') {
       message = 'None of the requested configurations were supported.';
     }
+
+    // According to the spec, this should be a DOMException, but there is not a
+    // public constructor for that.  So we make this look-alike instead.
     const unsupportedError = new Error(message);
     unsupportedError.name = 'NotSupportedError';
-    unsupportedError.code = DOMException.NOT_SUPPORTED_ERR;
+    unsupportedError['code'] = DOMException.NOT_SUPPORTED_ERR;
     throw unsupportedError;
   }
 
@@ -411,19 +414,24 @@ shaka.polyfill.PatchedMediaKeysWebkit.MediaKeys = class {
 
   /**
    * @param {!MediaKeyEvent} event
+   * @suppress {constantProperty} We reassign what would be const on a real
+   *   MediaEncryptedEvent, but in our look-alike event.
    * @private
    */
   onWebkitNeedKey_(event) {
     shaka.log.debug('PatchedMediaKeysWebkit.onWebkitNeedKey_', event);
     goog.asserts.assert(this.media_, 'media_ not set in onWebkitNeedKey_');
 
     const event2 =
-    /** @type {!CustomEvent} */ (document.createEvent('CustomEvent'));
+      /** @type {!CustomEvent} */ (document.createEvent('CustomEvent'));
     event2.initCustomEvent('encrypted', false, false, null);
 
-    // not used by v0.1b EME, but given a valid value
-    event2.initDataType = 'webm';
-    event2.initData = event.initData;
+    const encryptedEvent =
+      /** @type {!MediaEncryptedEvent} */(/** @type {?} */(event2));
+    // initDataType is not used by v0.1b EME, so any valid value is fine here.
+    encryptedEvent.initDataType = 'cenc';
+    encryptedEvent.initData = shaka.util.BufferUtils.toArrayBuffer(
+        event.initData);
 
     this.media_.dispatchEvent(event2);
   }
@@ -603,20 +611,19 @@ class extends shaka.util.FakeEventTarget {
     // will at least provide some information which can be used to look into the
     // problem.
     const error = new Error('EME v0.1b key error');
-    error.errorCode = event.errorCode;
-    error.errorCode.systemCode = event.systemCode;
+    const errorCode = event.errorCode;
+    errorCode.systemCode = event.systemCode;
+    error['errorCode'] = errorCode;
 
     // The presence or absence of sessionId indicates whether this corresponds
     // to generateRequest() or update().
     if (!event.sessionId && this.generatePromise_) {
-      error.method = 'generateRequest';
       if (event.systemCode == 45) {
         error.message = 'Unsupported session type.';
       }
       this.generatePromise_.reject(error);
       this.generatePromise_ = null;
     } else if (event.sessionId && this.updatePromise_) {
-      error.method = 'update';
       this.updatePromise_.reject(error);
       this.updatePromise_ = null;
     } else {