Add interfaces/compression.idl and test (web-platform-tests#23846)

Closes web-platform-tests#23829

compression/idlharness.https.any.js

@@ -0,0 +1,17 @@
+// META: script=/resources/WebIDLParser.js
+// META: script=/resources/idlharness.js
+
+'use strict';
+
+// https://wicg.github.io/compression/
+
+idl_test(
+  ['compression'],
+  [],
+  idl_array => {
+    idl_array.add_objects({
+      CompressionStream: ['new CompressionStream("deflate")'],
+      DecompressionStream: ['new DecompressionStream("deflate")'],
+    });
+  }
+);

interfaces/compression.idl

@@ -0,0 +1,21 @@
+// GENERATED CONTENT - DO NOT EDIT
+// Content was automatically extracted by Reffy into reffy-reports
+// (https://github.com/tidoust/reffy-reports)
+// Source: Compression Streams (https://wicg.github.io/compression/)
+
+interface mixin GenericTransformStream {
+  readonly attribute ReadableStream readable;
+  readonly attribute WritableStream writable;
+};
+
+[Exposed=(Window,Worker)]
+interface CompressionStream {
+  constructor(DOMString format);
+};
+CompressionStream includes GenericTransformStream;
+
+[Exposed=(Window,Worker)]
+interface DecompressionStream {
+  constructor(DOMString format);
+};
+DecompressionStream includes GenericTransformStream;