Bug 1837078 - Do not get language id payload if the page is hidden; r=nordzilla

This also removes some dead code around clearing the language tag, and
properly lists the required events for the TranslationsChild. I guess
that code was never even running, and I tests it manually after removing
it.

Differential Revision: https://phabricator.services.mozilla.com/D180885

toolkit/components/translations/actors/TranslationsChild.sys.mjs

@@ -20,24 +20,25 @@ export class TranslationsChild extends JSWindowActorChild {
    */
   innerWindowId = null;
   isDestroyed = false;
-  #areLangTagsReported = false;
+  #isPageHidden = false;
   #wasTranslationsEngineCreated = false;
 
   handleEvent(event) {
     switch (event.type) {
       case "DOMContentLoaded":
-        this.innerWindowId = this.contentWindow.windowGlobalChild.innerWindowId;
+        this.innerWindowId =
+          this.contentWindow?.windowGlobalChild.innerWindowId;
         if (!this.#isRestrictedPage()) {
-          this.#areLangTagsReported = true;
           this.sendAsyncMessage("Translations:ReportLangTags", {
             documentElementLang: this.document.documentElement.lang,
           });
         }
         break;
+      case "pageshow":
+        this.#isPageHidden = false;
+        break;
       case "pagehide":
-        if (this.#areLangTagsReported) {
-          this.sendAsyncMessage("Translations:ClearLangTags");
-        }
+        this.#isPageHidden = true;
         break;
     }
   }
@@ -47,6 +48,9 @@ export class TranslationsChild extends JSWindowActorChild {
    * about:* pages will not be translated.
    */
   #isRestrictedPage() {
+    if (!this.contentWindow?.location) {
+      return true;
+    }
     const { href } = this.contentWindow.location;
     // Keep this logic up to date with TranslationsParent.isRestrictedPage.
     return !(
@@ -141,9 +145,12 @@ export class TranslationsChild extends JSWindowActorChild {
   }
 
   createLanguageIdEngine() {
-    return lazy.LanguageIdEngine.getOrCreate(() =>
-      this.sendQuery("Translations:GetLanguageIdEnginePayload")
-    );
+    return lazy.LanguageIdEngine.getOrCreate(() => {
+      if (this.#isPageHidden) {
+        throw new Error("The page was already hidden.");
+      }
+      return this.sendQuery("Translations:GetLanguageIdEnginePayload");
+    });
   }
 
   createTranslationsEngine(fromLanguage, toLanguage) {

toolkit/components/translations/actors/TranslationsParent.sys.mjs

@@ -456,10 +456,6 @@ export class TranslationsParent extends JSWindowActorParent {
       case "Translations:GetPreferredLanguages": {
         return TranslationsParent.getPreferredLanguages();
       }
-      case "Translations:ClearLangTags": {
-        this.languageState.detectedLanguages = null;
-        return undefined;
-      }
       case "Translations:ReportLangTags": {
         const { documentElementLang, href } = data;
         const detectedLanguages = await this.getDetectedLanguages(

toolkit/modules/ActorManagerParent.sys.mjs

@@ -489,9 +489,8 @@ let JSWINDOWACTORS = {
     child: {
       esModuleURI: "resource://gre/actors/TranslationsChild.sys.mjs",
       events: {
+        pagehide: {},
         pageshow: {},
-        DOMHeadElementParsed: {},
-        DOMDocElementInserted: {},
         DOMContentLoaded: {},
       },
     },