fix(events): avoid firing lifecycle events twice (#16055)

Previously, when some iframe started/finished a new navigation, we
could have removed and then re-addded load/domcontentloaded on the
main frame.

Drive-by: unflake wheel test in Firefox.

packages/playwright-core/src/server/frames.ts

@@ -530,7 +530,7 @@ export class Frame extends SdkObject {
   _onClearLifecycle() {
     this._firedLifecycleEvents.clear();
     // Recalculate subtree lifecycle for the whole tree - it should not be that big.
-    this._page.mainFrame()._recalculateLifecycle();
+    this._page.mainFrame()._recalculateLifecycle(this);
     // Keep the current navigation request if any.
     this._inflightRequests = new Set(Array.from(this._inflightRequests).filter(request => request === this._currentDocument.request));
     this._stopNetworkIdleTimer();
@@ -593,10 +593,10 @@ export class Frame extends SdkObject {
     });
   }
 
-  _recalculateLifecycle() {
+  _recalculateLifecycle(frameThatAllowsRemovingLifecycleEvents?: Frame) {
     const events = new Set<types.LifecycleEvent>(this._firedLifecycleEvents);
     for (const child of this._childFrames) {
-      child._recalculateLifecycle();
+      child._recalculateLifecycle(frameThatAllowsRemovingLifecycleEvents);
       // We require a particular lifecycle event to be fired in the whole
       // frame subtree, and then consider it done.
       for (const event of events) {
@@ -604,6 +604,12 @@ export class Frame extends SdkObject {
           events.delete(event);
       }
     }
+    if (frameThatAllowsRemovingLifecycleEvents !== this) {
+      // Usually, lifecycle events are fired once and not removed after that, so we keep existing ones.
+      // However, when we clear them right before a new commit, this is allowed for a particular frame.
+      for (const event of this._subtreeLifecycleEvents)
+        events.add(event);
+    }
     const mainFrame = this._page.mainFrame();
     for (const event of events) {
       // Checking whether we have already notified about this event.

tests/page/page-event-load.spec.ts

@@ -30,7 +30,7 @@ it('should fire once', async ({ page, server, browserName }) => {
 
 it('should fire once with iframe navigation', async ({ page, server, browserName }) => {
   it.info().annotations.push({ type: 'issue', description: 'https://github.com/microsoft/playwright/issues/15086' });
-  it.fail();
+  it.fixme(browserName === 'firefox', 'Firefox sometimes double fires.');
 
   let requestCount = 0;
   server.setRoute('/tracker', (_, res) => {

tests/page/wheel.spec.ts

@@ -148,6 +148,9 @@ it('should work when the event is canceled', async ({ page }) => {
   await page.evaluate(() => {
     document.querySelector('div').addEventListener('wheel', e => e.preventDefault());
   });
+  // Give wheel listener a chance to propagate through all the layers in Firefox.
+  for (let i = 0; i < 10; i++)
+    await page.evaluate(() => new Promise(x => requestAnimationFrame(() => requestAnimationFrame(x))));
   await page.mouse.wheel(0, 100);
   await expectEvent(page, {
     deltaX: 0,