Auto merge of #19511 - DonatJR:implement-read-methods-on-filereadersync, r=jdm

Implement read methods on FileReaderSync

<!-- Please describe your changes on the following line: -->
Implemented the read methods on the FileReaderSync struct according to https://w3c.github.io/FileAPI/#dfn-FileReaderSync

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #15114

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- [x] There are tests for these changes

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tests/wpt/metadata/FileAPI/FileReaderSync.worker.js.ini

@@ -1,11 +0,0 @@
-[FileReaderSync.worker.html]
-  type: testharness
-  [readAsText]
-    expected: FAIL
-
-  [readAsDataURL]
-    expected: FAIL
-
-  [readAsArrayBuffer]
-    expected: FAIL
-

tests/wpt/metadata/MANIFEST.json

@@ -409016,7 +409016,7 @@
    "testharness"
   ],
   "FileAPI/FileReaderSync.worker.js": [
-   "19741fbd0498bf9135408ceb6128221cbeb4e2f3",
+   "9d9a2b77b7fbd8ad4edb75228bd7bca1f915ad61",
    "testharness"
   ],
   "FileAPI/OWNERS": [

tests/wpt/web-platform-tests/FileAPI/FileReaderSync.worker.js

@@ -1,28 +1,56 @@
 importScripts("/resources/testharness.js");
 
-var blob, readerSync;
-setup(function() {
-  readerSync = new FileReaderSync();
-  blob = new Blob(["test"]);
+var blob, empty_blob, readerSync;
+setup(() => {
+    readerSync = new FileReaderSync();
+    blob = new Blob(["test"]);
+    empty_blob = new Blob();
 });
 
-test(function() {
-  assert_true(readerSync instanceof FileReaderSync);
+test(() => {
+    assert_true(readerSync instanceof FileReaderSync);
 }, "Interface");
 
-test(function() {
-  var text = readerSync.readAsText(blob);
-  assert_equals(text, "test");
+test(() => {
+    var text = readerSync.readAsText(blob);
+    assert_equals(text, "test");
 }, "readAsText");
 
-test(function() {
-  var data = readerSync.readAsDataURL(blob);
-  assert_equals(data.indexOf("data:"), 0);
+test(() => {
+    var text = readerSync.readAsText(empty_blob);
+    assert_equals(text, "");
+}, "readAsText with empty blob");
+
+test(() => {
+    var data = readerSync.readAsDataURL(blob);
+    assert_equals(data.indexOf("data:"), 0);
 }, "readAsDataURL");
 
-test(function() {
-  var data = readerSync.readAsArrayBuffer(blob);
-  assert_true(data instanceof ArrayBuffer);
+test(() => {
+    var data = readerSync.readAsDataURL(empty_blob);
+    assert_equals(data.indexOf("data:"), 0);
+}, "readAsDataURL with empty blob");
+
+test(() => {
+    var data = readerSync.readAsBinaryString(blob);
+    assert_equals(data, "test");
+}, "readAsBinaryString");
+
+test(() => {
+    var data = readerSync.readAsBinaryString(empty_blob);
+    assert_equals(data, "");
+}, "readAsBinaryString with empty blob");
+
+test(() => {
+    var data = readerSync.readAsArrayBuffer(blob);
+    assert_true(data instanceof ArrayBuffer);
+    assert_equals(data.byteLength, "test".length);
 }, "readAsArrayBuffer");
 
+test(() => {
+    var data = readerSync.readAsArrayBuffer(empty_blob);
+    assert_true(data instanceof ArrayBuffer);
+    assert_equals(data.byteLength, 0);
+}, "readAsArrayBuffer with empty blob");
+
 done();