[api-minor] Move to Fluent for the localization (bug 1858715)

- For the generic viewer we use @fluent/dom and @fluent/bundle
- For the builtin pdf viewer in Firefox, we set a localization url
  and then we rely on document.l10n which is a DOMLocalization object.

.eslintrc

@@ -42,7 +42,7 @@
     "import/no-mutable-exports": "error",
     "import/no-self-import": "error",
     "import/no-unresolved": ["error", {
-      "ignore": ["display", "pdfjs", "pdfjs-lib", "pdfjs-web", "web"]
+      "ignore": ["display", "pdfjs", "pdfjs-lib", "pdfjs-web", "web", "fluent-bundle", "fluent-dom", ],
     }],
     "mozilla/avoid-removeChild": "error",
     "mozilla/use-includes-instead-of-indexOf": "error",

examples/mobile-viewer/viewer.js

@@ -97,26 +97,26 @@ const PDFViewerApplication = {
         if (exception instanceof pdfjsLib.InvalidPDFException) {
           // change error message also for other builds
           loadingErrorMessage = l10n.get(
-            "invalid_file_error",
+            "pdfjs-invalid-file-error",
             null,
             "Invalid or corrupted PDF file."
           );
         } else if (exception instanceof pdfjsLib.MissingPDFException) {
           // special message for missing PDFs
           loadingErrorMessage = l10n.get(
-            "missing_file_error",
+            "pdfjs-missing-file-error",
             null,
             "Missing PDF file."
           );
         } else if (exception instanceof pdfjsLib.UnexpectedResponseException) {
           loadingErrorMessage = l10n.get(
-            "unexpected_response_error",
+            "pdfjs-unexpected-response-error",
             null,
             "Unexpected server response."
           );
         } else {
           loadingErrorMessage = l10n.get(
-            "loading_error",
+            "pdfjs-loading-error",
             null,
             "An error occurred while loading the PDF."
           );
@@ -234,7 +234,7 @@ const PDFViewerApplication = {
     const l10n = this.l10n;
     const moreInfoText = [
       l10n.get(
-        "error_version_info",
+        "pdfjs-error-version-info",
         { version: pdfjsLib.version || "?", build: pdfjsLib.build || "?" },
         "PDF.js v{{version}} (build: {{build}})"
       ),
@@ -243,20 +243,24 @@ const PDFViewerApplication = {
     if (moreInfo) {
       moreInfoText.push(
         l10n.get(
-          "error_message",
+          "pdfjs-error-message",
           { message: moreInfo.message },
           "Message: {{message}}"
         )
       );
       if (moreInfo.stack) {
         moreInfoText.push(
-          l10n.get("error_stack", { stack: moreInfo.stack }, "Stack: {{stack}}")
+          l10n.get(
+            "pdfjs-error-stack",
+            { stack: moreInfo.stack },
+            "Stack: {{stack}}"
+          )
         );
       } else {
         if (moreInfo.filename) {
           moreInfoText.push(
             l10n.get(
-              "error_file",
+              "pdfjs-error-file",
               { file: moreInfo.filename },
               "File: {{file}}"
             )
@@ -265,7 +269,7 @@ const PDFViewerApplication = {
         if (moreInfo.lineNumber) {
           moreInfoText.push(
             l10n.get(
-              "error_line",
+              "pdfjs-error-line",
               { line: moreInfo.lineNumber },
               "Line: {{line}}"
             )

external/importL10n/locales.mjs

@@ -70,7 +70,7 @@ function downloadLanguageFiles(root, langCode) {
   const MOZ_CENTRAL_PDFJS_DIR = "/raw-file/default/browser/pdfviewer/";
 
   // Defines which files to download for each language.
-  const files = ["viewer.properties"];
+  const files = ["viewer.ftl"];
   let downloadsLeft = files.length;
 
   const outputDir = path.join(root, langCode);