Code review re. dynamically loaded vapi-client-extra.js

Related commit:
- 87d0e456f1

Ensure that the code which depends on extending
`vapi-client.js` is ready to deal with
`vapi-client-extra.js` failing to load.

platform/chromium/vapi-client.js

@@ -79,6 +79,7 @@ vAPI.messaging = {
     port: null,
     portTimer: null,
     portTimerDelay: 10000,
+    extended: undefined,
     extensions: [],
     msgIdGenerator: 1,
     pending: new Map(),
@@ -219,6 +220,19 @@ vAPI.messaging = {
         port.postMessage({ channel, msgId, msg });
         return promise;
     },
+
+    // Dynamically extend capabilities.
+    extend: function() {
+        if ( this.extended === undefined ) {
+            this.extended = vAPI.messaging.send('vapi', {
+                what: 'extendClient'
+            }).then(( ) => {
+                return vAPI instanceof Object && this.extensions.length !== 0;
+            }).catch(( ) => {
+            });
+        }
+        return this.extended;
+    },
 };
 
 vAPI.shutdown.add(( ) => {

src/js/scriptlets/cosmetic-logger.js

@@ -303,11 +303,8 @@ const handlers = {
 
 /******************************************************************************/
 
-(async ( ) => {
-    // Dynamically add broadcast listening abilities.
-    if ( vAPI.broadcastListener instanceof Object === false ) {
-        await vAPI.messaging.send('vapi', { what: 'extendClient' });
-    }
+vAPI.messaging.extend().then(extended => {
+    if ( extended !== true ) { return; }
     const broadcastListener = msg => {
         if ( msg.what === 'loggerDisabled' ) {
             processTimer.clear();
@@ -318,7 +315,7 @@ const handlers = {
         }
     };
     vAPI.broadcastListener.add(broadcastListener);
-})();
+});
 
 vAPI.domWatcher.addListener(handlers);
 

src/js/scriptlets/dom-inspector.js

@@ -884,7 +884,7 @@ const onMessage = function(request) {
 
 // Install DOM inspector widget
 
-const bootstrap = async function(ev) {
+const bootstrap = function(ev) {
     if ( ev ) {
         pickerRoot.removeEventListener(ev.type, bootstrap);
     }
@@ -934,9 +934,8 @@ const bootstrap = async function(ev) {
 
     // Dynamically add direct connection abilities so that we can establish
     // a direct, fast messaging connection to the logger.
-    if ( vAPI.MessagingConnection instanceof Function === false ) {
-        await vAPI.messaging.send('vapi', { what: 'extendClient' });
-    }
+    vAPI.messaging.extend().then(extended => {
+        if ( extended !== true ) { return; }
         vAPI.MessagingConnection.connectTo('domInspector', 'loggerUI', msg => {
             switch ( msg.what ) {
             case 'connectionAccepted':
@@ -951,6 +950,7 @@ const bootstrap = async function(ev) {
                 break;
             }
         });
+    });
 };
 
 pickerRoot = document.createElement('iframe');