test: add test for ContentWorkarounds (#5123)

Adds simple test to ensure `fakeEncryption()` adds encv/enca box
correctly.

test/media/content_workarounds_unit.js

@@ -0,0 +1,43 @@
+/*! @license
+ * Shaka Player
+ * Copyright 2016 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+describe('ContentWorkarounds', () => {
+  const encryptionBoxes = {
+    'encv': ['hev1', 'hvc1', 'avc1', 'avc3'],
+    'enca': ['ac-3', 'ec-3', 'mp4a'],
+  };
+  for (const encryptionBox of Object.keys(encryptionBoxes)) {
+    for (const box of encryptionBoxes[encryptionBox]) {
+      it(`adds ${encryptionBox} box for ${box}`, () => {
+        const boxType = [];
+        for (const char of box) {
+          boxType.push(char.charCodeAt(0));
+        }
+        const unencrypted = new Uint8Array([
+          0x00, 0x00, 0x00, 0x20, // size
+          0x73, 0x74, 0x73, 0x64, // stsd
+          0x01,                   // version
+          0x12, 0x34, 0x56,       // flags
+          0x00, 0x00, 0x00, 0x01, // count
+          0x00, 0x00, 0x00, 0x10, // size
+          ...boxType,             // box type
+          0x01,                   // version
+          0x12, 0x34, 0x56,       // flags
+          0x00, 0x11, 0x22, 0x33, // payload
+        ]);
+
+        const faked =
+            shaka.media.ContentWorkarounds.fakeEncryption(unencrypted);
+        const spy = jasmine.createSpy('boxCallback');
+        new shaka.util.Mp4Parser()
+            .fullBox('stsd', shaka.util.Mp4Parser.sampleDescription)
+            .box(encryptionBox, /** @type {!Function} */ (spy))
+            .parse(faked);
+        expect(spy).toHaveBeenCalled();
+      });
+    }
+  }
+});