feat: Add support for changing codecs in MediaSourceEngine (shaka-pro…

…ject#5217)

Thanks to shaka-project#4766

This PR adds support for codec hot-switching in MediaSourceEngine. 
There are two ways to change codec:
- Using `Sourcebuffer.changeType` on supported browsers 
- Reloading the `MediaSource` instance with the new codecs

This change does not change the current filter logic, so this code is
not used yet. The change in the filtering will be done in a subsequent
PR in order to simplify the changes of this PR.

lib/media/media_source_capabilities.js

@@ -27,6 +27,16 @@ shaka.media.Capabilities = class {
     supportMap.set(type, currentSupport);
     return currentSupport;
   }
+
+  /**
+   * Determine support for SourceBuffer.changeType
+   * @return {boolean}
+   */
+  static isChangeTypeSupported() {
+    return !!window.SourceBuffer &&
+        // eslint-disable-next-line no-restricted-syntax
+        !!SourceBuffer.prototype && !!SourceBuffer.prototype.changeType;
+  }
 };
 
 /**