Move test for `requestId` property into `isMessage` function

Since all message types now include this property, we can check for it
in `isMessage` instead of requiring a separate check.

src/shared/messaging/port-provider.js

@@ -139,7 +139,7 @@ export class PortProvider {
     const handleRequest = event => {
       const { data, origin, source } = /** @type {MessageEvent} */ (event);
 
-      if (!isMessage(data) || data.type !== 'request' || !data.requestId) {
+      if (!isMessage(data) || data.type !== 'request') {
         // If this does not look like a message intended for us, ignore it.
         return;
       }

src/shared/messaging/port-util.js

@@ -24,7 +24,7 @@ export function isMessage(data) {
     return false;
   }
 
-  for (let property of ['frame1', 'frame2', 'type']) {
+  for (let property of ['frame1', 'frame2', 'type', 'requestId']) {
     if (typeof data[property] !== 'string') {
       return false;
     }

src/shared/messaging/test/port-util-test.js

@@ -14,6 +14,7 @@ describe('port-util', () => {
         frame1: 'guest',
         frame2: 'sidebar',
         type: 'request',
+        requestId: 'bar',
         extraField: 'foo',
       },
     ].forEach(data => {
@@ -27,7 +28,15 @@ describe('port-util', () => {
       undefined,
       {},
       'str',
-      { frame1: 'guest', frame2: false, type: 'request' },
+
+      // Wrong type for a property
+      { frame1: 'guest', frame2: false, type: 'request', requestId: 'bar' },
+
+      // Missing properties
+      { frame2: 'sidebar', type: 'request', requestId: 'r1' }, // Missing 'frame1'
+      { frame1: 'guest', type: 'request', requestId: 'r1' }, // Missing 'frame2'
+      { frame1: 'guest', frame2: 'sidebar', requestId: 'r1' }, // Missing 'type'
+      { frame1: 'guest', frame2: 'sidebar', type: 'request' }, // Missing 'requestId'
     ].forEach(data => {
       it('returns false if data is not a valid message', () => {
         assert.isFalse(isMessage(data));

src/sidebar/services/test/frame-sync-test.js

@@ -171,6 +171,7 @@ describe('FrameSyncService', () => {
         frame1: 'guest',
         frame2: 'sidebar',
         type: 'offer',
+        requestId: 'abc',
       },
       [port1]
     );