Replace hide-scrollbars flag with a web setting.

chromecast/browser/cast_content_browser_client.cc

Index: chromecast/browser/cast_content_browser_client.cc
diff --git a/chromecast/browser/cast_content_browser_client.cc b/chromecast/browser/cast_content_browser_client.cc
index a4b1d4034aa6735fb3b20408a8d125053df795a0..473b16d29fe21b502961cf44501cda10b77fdf80 100644
--- a/chromecast/browser/cast_content_browser_client.cc
+++ b/chromecast/browser/cast_content_browser_client.cc
@@ -292,6 +292,8 @@ void CastContentBrowserClient::OverrideWebkitPrefs(
   // Enable 5% margins for WebVTT cues to keep within title-safe area
   prefs->text_track_margin_percentage = 5;
 
+  prefs->hide_scrollbars = true;
+
 #if defined(OS_ANDROID)
   // Enable the television style for viewport so that all cast apps have a
   // 1280px wide layout viewport by default.