feat: Implement basic windows linux support

windows/runner/flutter_window.cpp

@@ -0,0 +1,29 @@
+#include "flutter_window.h"
+
+#include "flutter/generated_plugin_registrant.h"
+
+FlutterWindow::FlutterWindow(RunLoop* run_loop,
+                             const flutter::DartProject& project)
+    : run_loop_(run_loop), project_(project) {}
+
+FlutterWindow::~FlutterWindow() {}
+
+void FlutterWindow::OnCreate() {
+  Win32Window::OnCreate();
+
+  // The size here is arbitrary since SetChildContent will resize it.
+  flutter_controller_ =
+      std::make_unique<flutter::FlutterViewController>(100, 100, project_);
+  RegisterPlugins(flutter_controller_.get());
+  run_loop_->RegisterFlutterInstance(flutter_controller_.get());
+  SetChildContent(flutter_controller_->view()->GetNativeWindow());
+}
+
+void FlutterWindow::OnDestroy() {
+  if (flutter_controller_) {
+    run_loop_->UnregisterFlutterInstance(flutter_controller_.get());
+    flutter_controller_ = nullptr;
+  }
+
+  Win32Window::OnDestroy();
+}