Protocol-specific network handling

When implementing custom network protocol behavior, ensure that modifications are properly scoped to only the intended protocol types and include upstream context documentation. Avoid applying protocol-specific changes broadly across all network protocols, as this can break assumptions and cause unintended side effects.

Key principles:

1. Scope restrictions appropriately: Limit custom behavior to specific protocol types that require it, rather than applying changes universally
2. Document upstream context: Include references to upstream changes and their motivations in patch files for future maintainability
3. Align with upstream behavior: Keep behavior consistent with upstream implementations except where explicitly needed for specific protocols

Example from streaming protocol handling:

// Good: Scoped to streaming custom protocols only
if (IsStreamingCustomProtocol(url)) {
  destination_url_data->set_range_supported();
}

// Avoid: Broad application that could break other protocols
destination_url_data->set_range_supported(); // Applied to all protocols

When modifying network service initialization, ensure proper guards are in place:

SystemNetworkContextManager* SystemNetworkContextManager::GetInstance() {
  if (!g_system_network_context_manager) {
    content::GetNetworkService();
    DCHECK(g_system_network_context_manager);
  }
  return g_system_network_context_manager;
}

This approach prevents breaking buffering assumptions for protocols like file:// URLs while enabling the required functionality for custom streaming protocols that support range requests.