[Android] Added a runtime flag to enable autoplay of muted videos.

content/browser/renderer_host/render_view_host_impl.cc

Index: content/browser/renderer_host/render_view_host_impl.cc
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index 8f35c7c67dbd3b70369056a80aa634e6f511d5ff..4e847b986e4acda1633ee587f21115a5617b20f1 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -428,6 +428,8 @@ WebPreferences RenderViewHostImpl::ComputeWebkitPrefs() {
   prefs.user_gesture_required_for_media_playback = !command_line.HasSwitch(
       switches::kDisableGestureRequirementForMediaPlayback) &&
           (autoplay_group_name.empty() || autoplay_group_name != "Enabled");
+  prefs.videos_as_images_enabled = command_line.HasSwitch(
+      switches::kEnableVideosAsImages);
 #endif
 
   // Handle autoplay gesture override experiment.