Update media_app to DdHwDgGvGlyPA2ih4uxWvn5jmuug258Nz1wrbgcJHQ8C CIPD package.

Also rolls in changes from crrev/c/2257468: Add a stub for mediaApp.AbstractFileList.addObserver().
This is needed to prevent browser test breakages due to missing API.

CIPD package: https://chrome-infra-packages.appspot.com/p/chromeos_internal/apps/media_app/app/+/DdHwDgGvGlyPA2ih4uxWvn5jmuug258Nz1wrbgcJHQ8C

Release notes: http://go/media_app-x20/relnotes/Stable/media_app_202006220800_RC00.html

Bug: b/155461713, b/157949149, b/156201188, b/158043802, b/159567887, b/153594459

Cq-Include-Trybots: chrome/try:linux-chromeos-chrome
Change-Id: I66f094fd55fb37e2b62faf72218a94f23d7ae6ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2257464Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Trent Apted <tapted@chromium.org>
Commit-Queue: Bugs Nash <bugsnash@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781167}

DEPS

@@ -1543,7 +1543,7 @@ deps = {
     'packages': [
       {
         'package': 'chromeos_internal/apps/media_app/app',
-        'version': 'hHNzH9agD69T1E_LZpIZVzqyspiBI3MkAir2tP-KXtIC',
+        'version': 'DdHwDgGvGlyPA2ih4uxWvn5jmuug258Nz1wrbgcJHQ8C',
       },
     ],
     'condition': 'checkout_chromeos and checkout_src_internal',

chromeos/components/media_app_ui/resources/js/media_app.externs.js

@@ -105,6 +105,11 @@ mediaApp.AbstractFileList.prototype.loadNext = function() {};
  * @return {!Promise<undefined>}
  */
 mediaApp.AbstractFileList.prototype.loadPrev = function() {};
+/**
+ * @param {function(!mediaApp.AbstractFileList): void} observer invoked when the
+ *     size or contents of the file list changes.
+ */
+mediaApp.AbstractFileList.prototype.addObserver = function(observer) {};
 
 /**
  * The delegate which exposes open source privileged WebUi functions to

chromeos/components/media_app_ui/resources/js/receiver.js

@@ -121,6 +121,11 @@ class ReceivedFileList {
   async loadPrev() {
     await parentMessagePipe.sendMessage(Message.NAVIGATE, {direction: -1});
   }
+
+  /** @override */
+  addObserver(observer) {
+    // TODO(b/158043802): Implement me.
+  }
 }
 
 parentMessagePipe.registerHandler(Message.LOAD_FILES, async (message) => {