Fix the issue causing the screen to be black after resuming when in low processor mode.

This is done by forcing a redraw and buffers swap when resuming the app.

platform/android/java_godot_lib_jni.cpp

@@ -514,6 +514,8 @@ JNIEXPORT void JNICALL Java_org_godotengine_godot_GodotLib_onRendererResumed(JNI
 	if (step.get() <= 0)
 		return;
 
+	// We force redraw to ensure we render at least once when resuming the app.
+	Main::force_redraw();
 	if (os_android->get_main_loop()) {
 		os_android->get_main_loop()->notification(MainLoop::NOTIFICATION_APP_RESUMED);
 	}

platform/android/os_android.cpp

@@ -322,10 +322,11 @@ void OS_Android::main_loop_begin() {
 bool OS_Android::main_loop_iterate(bool *r_should_swap_buffers) {
 	if (!main_loop)
 		return false;
+	uint64_t current_frames_drawn = Engine::get_singleton()->get_frames_drawn();
 	bool exit = Main::iteration();
 
 	if (r_should_swap_buffers) {
-		*r_should_swap_buffers = !is_in_low_processor_usage_mode() || _update_pending;
+		*r_should_swap_buffers = !is_in_low_processor_usage_mode() || _update_pending || current_frames_drawn != Engine::get_singleton()->get_frames_drawn();
 	}
 
 	return exit;