Do not expose getDisplayMedia() on Android.

This feature is not supported on Android, so it is better not to expose
it so that JavaScript-side feature detection works correctly.

Bug: 1038244
Change-Id: I3faf65062113e164ef37995bc6a556227f72b5cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2030466
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Auto-Submit: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736822}

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -794,7 +794,7 @@
     },
     {
       name: "GetDisplayMedia",
-      status: "stable",
+      status: {"Android": "", "default": "stable"},
     },
     {
       name: "GroupEffect",