[Fuchsia] Allow web_engine_shell to autoplay videos.

Bug: 1148926
Change-Id: I7b1c44967147d3674479544871973f9b39032bca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2538163
Commit-Queue: Chong Gu <chonggu@google.com>
Auto-Submit: Chong Gu <chonggu@google.com>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827425}

fuchsia/engine/test/web_engine_shell.cc

@@ -221,6 +221,7 @@ int main(int argc, char** argv) {
 
   // Create the browser |frame| which will contain the webpage.
   fuchsia::web::CreateFrameParams frame_params;
+  frame_params.set_autoplay_policy(fuchsia::web::AutoplayPolicy::ALLOW);
   if (remote_debugging_port)
     frame_params.set_enable_remote_debugging(true);