chromecast: Disable images in C4A configuration

Images rendering is unnecessary in Cast for Audio only configuration.
So let's disable them from rendering.

Change-Id: Ibd6e0d20c8c6e2473b29fef5cae0cc18128b7599
Signed-off-by: Volodymyr Riazantsev <riazantsevv@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2042765Reviewed-by: Michael Spang <spang@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739417}

chromecast/browser/cast_content_browser_client.cc

@@ -516,6 +516,11 @@ void CastContentBrowserClient::OverrideWebkitPrefs(
 
   prefs->hide_scrollbars = true;
 
+  // Disable images rendering in Cast for Audio configuration
+#if BUILDFLAG(IS_CAST_AUDIO_ONLY)
+  prefs->images_enabled = false;
+#endif
+
 #if defined(OS_ANDROID)
   // Enable the television style for viewport so that all cast apps have a
   // 1280px wide layout viewport by default.