fix(bidi): expose main binding in existing page (#35997)

packages/playwright-core/src/server/bidi/bidiBrowser.ts

@@ -400,11 +400,26 @@ export class BidiBrowserContext extends BrowserContext {
         ownership: bidi.Script.ResultOwnership.Root,
       }
     }];
-    await this._browser._browserSession.send('script.addPreloadScript', {
-      functionDeclaration: `function addMainBinding(callback) { globalThis['${kPlaywrightBinding}'] = callback; }`,
+    const functionDeclaration = `function addMainBinding(callback) { globalThis['${kPlaywrightBinding}'] = callback; }`;
+    const promises = [];
+    promises.push(this._browser._browserSession.send('script.addPreloadScript', {
+      functionDeclaration,
       arguments: args,
       userContexts: [this._userContextId()],
-    });
+    }));
+    promises.push(...this._bidiPages().map(page => {
+      const realms = [...page._realmToContext].filter(([realm, context]) => context.world === 'main').map(([realm, context]) => realm);
+      return Promise.all(realms.map(realm => {
+        return page._session.send('script.callFunction', {
+          functionDeclaration,
+          arguments: args,
+          target: { realm },
+          awaitPromise: false,
+          userActivation: false,
+        });
+      }));
+    }));
+    await Promise.all(promises);
   }
 
   onClosePersistent() {}

packages/playwright-core/src/server/bidi/bidiPage.ts

@@ -46,7 +46,7 @@ export class BidiPage implements PageDelegate {
   readonly _page: Page;
   readonly _session: BidiSession;
   readonly _opener: BidiPage | null;
-  private readonly _realmToContext: Map<string, dom.FrameExecutionContext>;
+  readonly _realmToContext: Map<string, dom.FrameExecutionContext>;
   private _sessionListeners: RegisteredListener[] = [];
   readonly _browserContext: BidiBrowserContext;
   readonly _networkManager: BidiNetworkManager;