Own Windows tablet path and thin legacy web fallback

src/platform_legacy/legacy_platform_state.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "platform_api/platform_policy.h"
 #include "platform_api/platform_services.h"
 
 #if __LINUX__ || __WEB__
@@ -21,6 +22,14 @@ void request_legacy_glfw_app_close();
 #endif
 
 [[nodiscard]] pp::platform::WebPlatformServices& active_legacy_web_platform_services();
+[[nodiscard]] bool handles_legacy_web_platform_family(pp::platform::PlatformFamily family) noexcept;
+void publish_legacy_web_exported_image(std::string_view path);
+void flush_legacy_web_persistent_storage();
+[[nodiscard]] int default_legacy_web_canvas_resolution() noexcept;
+void save_legacy_web_prepared_file(
+    std::string_view path,
+    std::string_view suggested_name,
+    pp::platform::PreparedFileCallback callback);
 
 [[nodiscard]] const pp::platform::PlatformStoragePaths& active_legacy_storage_paths();
 void set_legacy_storage_paths(pp::platform::PlatformStoragePaths paths);