Use shorter arrow functions where possible

For arrow functions that are both simple and short, we can avoid using explicit `return` to shorten them even further without hurting readability.

For the `gulp mozcentral` build-target this reduces the overall size of the output by just under 1 kilo-byte (which isn't a lot but still can't hurt).

test/integration/freetext_editor_spec.mjs

@@ -237,9 +237,10 @@ describe("FreeText Editor", () => {
           await clearAll(page);
 
           for (const n of [0, 1, 2]) {
-            const hasEditor = await page.evaluate(sel => {
-              return !!document.querySelector(sel);
-            }, getEditorSelector(n));
+            const hasEditor = await page.evaluate(
+              sel => !!document.querySelector(sel),
+              getEditorSelector(n)
+            );
 
             expect(hasEditor).withContext(`In ${browserName}`).toEqual(false);
           }

test/unit/api_spec.js

@@ -942,14 +942,10 @@ describe("api", function () {
       );
 
       const loadingTask1 = getDocument(basicApiGetDocumentParams);
-      const promise1 = loadingTask1.promise.then(pdfDoc => {
-        return pdfDoc.numPages;
-      });
+      const promise1 = loadingTask1.promise.then(pdfDoc => pdfDoc.numPages);
 
       const loadingTask2 = getDocument(tracemonkeyGetDocumentParams);
-      const promise2 = loadingTask2.promise.then(pdfDoc => {
-        return pdfDoc.numPages;
-      });
+      const promise2 = loadingTask2.promise.then(pdfDoc => pdfDoc.numPages);
 
       const [numPages1, numPages2] = await Promise.all([promise1, promise2]);
       expect(numPages1).toEqual(3);
@@ -3901,9 +3897,9 @@ Caron Broadcasting, Inc., an Ohio corporation (“Lessee”).`)
             true
           );
           expect(
-            currentImgData.data.every((value, index) => {
-              return value === firstImgData.data[index];
-            })
+            currentImgData.data.every(
+              (value, index) => value === firstImgData.data[index]
+            )
           ).toEqual(true);
 
           if (i === NUM_PAGES_THRESHOLD) {

test/unit/cff_parser_spec.js

@@ -377,9 +377,7 @@ describe("CFFCompiler", function () {
     bytes = new Uint8Array(bytes);
     return new CFFParser(
       {
-        getBytes: () => {
-          return bytes;
-        },
+        getBytes: () => bytes,
       },
       {},
       SEAC_ANALYSIS_ENABLED

test/unit/message_handler_spec.js

@@ -24,9 +24,7 @@ import { MessageHandler } from "../../src/shared/message_handler.js";
 describe("message_handler", function () {
   // Sleep function to wait for sometime, similar to setTimeout but faster.
   function sleep(ticks) {
-    return Promise.resolve().then(() => {
-      return ticks && sleep(ticks - 1);
-    });
+    return Promise.resolve().then(() => ticks && sleep(ticks - 1));
   }
 
   describe("sendWithStream", function () {

test/unit/node_stream_spec.js

@@ -62,9 +62,7 @@ describe("node_stream", function () {
             const [start, end] = request.headers.range
               .split("=")[1]
               .split("-")
-              .map(x => {
-                return Number(x);
-              });
+              .map(x => Number(x));
             const stream = fs.createReadStream(filePath, { start, end });
             response.writeHead(206, {
               "Content-Type": "application/pdf",

test/unit/pdf_find_controller_spec.js

@@ -121,9 +121,7 @@ function testSearch({
       }
     }
 
-    const totalMatches = matchesPerPage.reduce((a, b) => {
-      return a + b;
-    });
+    const totalMatches = matchesPerPage.reduce((a, b) => a + b);
 
     if (updateFindControlState) {
       eventBus.on(

test/unit/scripting_spec.js

@@ -52,9 +52,9 @@ describe("Scripting", function () {
       send_queue.set(command, { command, value });
     };
     // eslint-disable-next-line no-unsanitized/method
-    const promise = import(sandboxBundleSrc).then(pdfjsSandbox => {
-      return pdfjsSandbox.QuickJSSandbox();
-    });
+    const promise = import(sandboxBundleSrc).then(pdfjsSandbox =>
+      pdfjsSandbox.QuickJSSandbox()
+    );
     sandbox = {
       createSandbox(data) {
         promise.then(sbx => sbx.create(data));