[Chromecast] Disable http cache for Cast.

Http cache was disabled before the network service migration because
there was no significant benefit. Disable now in the network service path.

Bug: b/144224349
Test: TBD
Change-Id: If6ce53548d13e9ba16ad92e075217f4673089e69
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1918720Reviewed-by: Luke Halliwell (slow) <halliwell@chromium.org>
Commit-Queue: Junbo Ke <juke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715581}

chromecast/browser/cast_network_contexts.cc

@@ -202,6 +202,7 @@ CastNetworkContexts::CreateDefaultNetworkContextParams() {
   network::mojom::NetworkContextParamsPtr network_context_params =
       network::mojom::NetworkContextParams::New();
 
+  network_context_params->http_cache_enabled = false;
   network_context_params->user_agent = GetUserAgent();
   network_context_params->accept_language =
       CastHttpUserAgentSettings::AcceptLanguage();