call onMessage.addListener only once

lib/single-file/processors/lazy/content/content-lazy-loader.js

@@ -35,9 +35,20 @@ this.singlefile.lib.processors.lazy.content.loader = this.singlefile.lib.process
 	const removeEventListener = (type, listener, options) => window.removeEventListener(type, listener, options);
 	const timeouts = new Map();
 
+	browser.runtime.onMessage.addListener(message => {
+		if (message.method == "singlefile.lazyTimeout.onTimeout") {
+			const timeoutData = timeouts.get(message.type);
+			if (timeoutData) {
+				timeouts.delete(message.type);
+				timeoutData.callback();
+			}
+		}
+	});
+
 	return {
 		process: async options => {
 			if (document.documentElement) {
+				timeouts.clear();
 				const maxScrollY = Math.max(document.documentElement.scrollHeight - (document.documentElement.clientHeight * 1.5), 0);
 				const maxScrollX = Math.max(document.documentElement.scrollWidth - (document.documentElement.clientWidth * 1.5), 0);
 				if (window.scrollY <= maxScrollY && window.scrollX <= maxScrollX) {
@@ -154,18 +165,11 @@ this.singlefile.lib.processors.lazy.content.loader = this.singlefile.lib.process
 
 	async function setAsyncTimeout(type, callback, delay) {
 		if (browser && browser.runtime && browser.runtime.sendMessage) {
-			if (!timeouts.get(type)) {
-				timeouts.set(type, callback);
+			if (!timeouts.get(type) || !timeouts.get(type).pending) {
+				const timeoutData = { callback, pending: true };
+				timeouts.set(type, timeoutData);
 				await browser.runtime.sendMessage({ method: "singlefile.lazyTimeout.setTimeout", type, delay });
-				const timeoutCallback = message => {
-					if (message.method == "singlefile.lazyTimeout.onTimeout" && message.type == type) {
-						browser.runtime.onMessage.removeListener(timeoutCallback);
-						callback();
-						return Promise.resolve({});
-					}
-				};
-				timeouts.delete(type, callback);
-				browser.runtime.onMessage.addListener(timeoutCallback);
+				timeoutData.pending = false;
 			}
 		} else {
 			const timeoutId = timeouts.get(type);