fix: Detect smooth codec switch support on Apple devices (#7678)

Author: tykus160

externs/managedmediasource.js

@@ -22,3 +22,9 @@ function ManagedMediaSource() {}
  * @return {boolean}
  */
 ManagedMediaSource.isTypeSupported = function(type) {};
+
+/**
+ * @constructor
+ * @extends {SourceBuffer}
+ */
+function ManagedSourceBuffer() {}

lib/media/media_source_capabilities.js

@@ -40,9 +40,10 @@ shaka.media.Capabilities = class {
    * @return {boolean}
    */
   static isChangeTypeSupported() {
-    return !!window.SourceBuffer &&
+    const sourceBuffer = window.ManagedSourceBuffer || window.SourceBuffer;
+    return !!sourceBuffer &&
         // eslint-disable-next-line no-restricted-syntax
-        !!SourceBuffer.prototype && !!SourceBuffer.prototype.changeType;
+        !!sourceBuffer.prototype && !!sourceBuffer.prototype.changeType;
   }
 };