[FIX] web_editor: process historyStepsBuffer

Before this commit, any history step received before the history is
fully synchronised (`historySyncFinished`), would not be processed.

As a fail safe, this commit adds a buffer that will be processed as
soon as the history synchronization is finished
(`historySyncFinished`).

task-3217719

X-original-commit: acb58f921721b162954146f3c5364cb26823265f
Part-of: odoo/odoo#114583

addons/web_editor/static/src/js/wysiwyg/wysiwyg.js

@@ -468,6 +468,7 @@ const Wysiwyg = Widget.extend({
             // Wether or not the history has been sent or received at least once.
             let historySyncAtLeastOnce = false;
             let historySyncFinished = false;
+            let historyStepsBuffer = [];
 
             return new PeerToPeer({
                 peerConnectionConfig: { iceServers: this._iceServers },
@@ -556,6 +557,11 @@ const Wysiwyg = Widget.extend({
                                         this.odooEditor.onExternalMultiselectionUpdate(remoteSelection);
                                     }
                                 }
+                                // In case there are steps received in the meantime, process them.
+                                if (historyStepsBuffer.length) {
+                                    this.odooEditor.onExternalHistorySteps(historyStepsBuffer);
+                                    historyStepsBuffer = [];
+                                }
                                 historySyncFinished = true;
                             } else {
                                 const remoteSelection = await this.ptp.requestClient(fromClientId, 'get_collaborative_selection', undefined, { transport: 'rtc' });
@@ -570,6 +576,8 @@ const Wysiwyg = Widget.extend({
                             // before the history has synced at least once.
                             if (historySyncFinished) {
                                 this.odooEditor.onExternalHistorySteps([notificationPayload]);
+                            } else {
+                                historyStepsBuffer.push(notificationPayload);
                             }
                             break;
                         case 'oe_history_set_selection': {