[Media Session] Update Android WebView expectations

Media Session API should not be available in Android
WebView so we should update expectations.

BUG=925700

Change-Id: I52330a6fa1d42501ea4bc75e32ddde26db349e72
Reviewed-on: https://chromium-review.googlesource.com/c/1440908Reviewed-by: Tim Volodine <timvolodine@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#627043}

android_webview/tools/system_webview_shell/test/data/webexposed/not-webview-exposed.txt

@@ -54,15 +54,20 @@ interface HTMLMediaElement : HTMLElement
     getter remote                      # crbug.com/521319
 
 # permissions API (crbug.com/490120), presentation API (crbug.com/521319),
-# share API (crbug.com/765923) and custom scheme handlers (crbug.com/589502)
-# not supported in webview
+# share API (crbug.com/765923), custom scheme handlers (crbug.com/589502)
+# and media session API (crbug.com/925997) are not supported in webview.
 interface Navigator
+    getter mediaSession                # crbug.com/925997
     getter permissions                 # crbug.com/490120
     getter presentation                # crbug.com/521319
     method registerProtocolHandler     # crbug.com/589502
     method unregisterProtocolHandler   # crbug.com/589502
     method share                       # crbug.com/765923
 
+# Media Session API is not enabled in Android WebView (crbug.com/925997)
+interface MediaMetadata
+interface MediaSession
+
 # notifications not yet supported in webview, crbug.com/551446
 interface ServiceWorkerRegistration : EventTarget
     getter pushManager