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

Implement read methods on FileReaderSync

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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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components/script/dom/webidls/DOMException.webidl

@@ -34,6 +34,7 @@ interface DOMException {
   const unsigned short TIMEOUT_ERR = 23;
   const unsigned short INVALID_NODE_TYPE_ERR = 24;
   const unsigned short DATA_CLONE_ERR = 25;
+  const unsigned short NOT_READABLE_ERR = 26;
 
   // Error code as u16
   readonly attribute unsigned short code;

components/script/dom/webidls/FileReaderSync.webidl

@@ -8,8 +8,12 @@
 interface FileReaderSync {
   // Synchronously return strings
 
-  // ArrayBuffer readAsArrayBuffer(Blob blob);
-  // DOMString readAsBinaryString(Blob blob);
-  // DOMString readAsText(Blob blob, optional DOMString label);
-  // DOMString readAsDataURL(Blob blob);
+  [Throws]
+  ArrayBuffer readAsArrayBuffer(Blob blob);
+  [Throws]
+  DOMString readAsBinaryString(Blob blob);
+  [Throws]
+  DOMString readAsText(Blob blob, optional DOMString label);
+  [Throws]
+  DOMString readAsDataURL(Blob blob);
 };