Fix flaky WKWebExtensionAPIWebRequest tests

https://bugs.webkit.org/show_bug.cgi?id=270824
rdar://124401551

Reviewed by Timothy Hatcher.

There were a few cascading issues here.

1) For webRequest, we were trying to create a persistent background page with manifest v3. This is not a supported
configuration, so it was being forced into being non-persistent.

This meant that the background page could sometimes unload, leading to the flakiness described in the bug.

2) After making this change, I discovered that we were attempting to load the background page before it was safe (before
moveLocalStorageIfNeeded was called).

To fix this, add a new variable tracking if it's safe to load the background view. This is set to true in loadBackgroundWebViewDuringLoad,
and checked in loadBackgroundWebViewIfNeeded before attempting to load the background web view.

* Source/WebKit/UIProcess/Extensions/Cocoa/WebExtensionContextCocoa.mm:
(WebKit::WebExtensionContext::loadBackgroundWebViewDuringLoad):
(WebKit::WebExtensionContext::loadBackgroundWebViewIfNeeded):
(WebKit::WebExtensionContext::loadBackgroundWebView):
* Source/WebKit/UIProcess/Extensions/WebExtensionContext.h:
(WebKit::WebExtensionContext::safeToLoadBackgroundContent const):
* Tools/TestWebKitAPI/Tests/WebKitCocoa/WKWebExtensionAPIWebRequest.mm:

Canonical link: https://commits.webkit.org/275955@main

Source/WebKit/UIProcess/Extensions/Cocoa/WebExtensionContextCocoa.mm

@@ -3013,6 +3013,7 @@ static _WKWebExtensionContextError toAPI(WebExtensionContext::Error error)
     if (!extension().hasBackgroundContent())
         return;
 
+    m_safeToLoadBackgroundContent = true;
     m_shouldFireStartupEvent = extensionController()->isFreshlyCreated();
 
     queueStartupAndInstallEventsForExtensionIfNecessary();
@@ -3041,7 +3042,7 @@ static _WKWebExtensionContextError toAPI(WebExtensionContext::Error error)
 {
     ASSERT(isLoaded());
 
-    if (!extension().hasBackgroundContent() || m_backgroundWebView)
+    if (!extension().hasBackgroundContent() || m_backgroundWebView || !safeToLoadBackgroundContent())
         return;
 
     loadBackgroundWebView();
@@ -3056,6 +3057,8 @@ static _WKWebExtensionContextError toAPI(WebExtensionContext::Error error)
 
     RELEASE_LOG_DEBUG(Extensions, "Loading background content");
 
+    ASSERT(safeToLoadBackgroundContent());
+
     ASSERT(!m_backgroundContentIsLoaded);
     m_backgroundContentIsLoaded = false;
 

Source/WebKit/UIProcess/Extensions/WebExtensionContext.h

@@ -446,6 +446,7 @@ class WebExtensionContext : public API::ObjectImpl<API::Object::Type::WebExtensi
 
     URL backgroundContentURL();
     WKWebView *backgroundWebView() const { return m_backgroundWebView.get(); }
+    bool safeToLoadBackgroundContent() const { return m_safeToLoadBackgroundContent; }
 
     bool decidePolicyForNavigationAction(WKWebView *, WKNavigationAction *);
     void didFinishNavigation(WKWebView *, WKNavigation *);
@@ -878,6 +879,7 @@ class WebExtensionContext : public API::ObjectImpl<API::Object::Type::WebExtensi
     std::unique_ptr<WebCore::Timer> m_unloadBackgroundWebViewTimer;
     MonotonicTime m_lastBackgroundPortActivityTime;
     bool m_backgroundContentIsLoaded { false };
+    bool m_safeToLoadBackgroundContent { false };
 
 #if ENABLE(INSPECTOR_EXTENSIONS)
     WeakHashMap<WebInspectorUIProxy, TabIdentifierWebViewPair> m_inspectorBackgroundPageMap;

Tools/TestWebKitAPI/Tests/WebKitCocoa/WKWebExtensionAPIWebRequest.mm

@@ -33,7 +33,7 @@
 
 #if PLATFORM(MAC)
 
-static auto *webRequestManifest = @{ @"manifest_version": @3, @"permissions": @[ @"webRequest" ], @"background": @{ @"scripts": @[ @"background.js" ], @"type": @"module", @"persistent": @YES } };
+static auto *webRequestManifest = @{ @"manifest_version": @2, @"permissions": @[ @"webRequest" ], @"background": @{ @"scripts": @[ @"background.js" ], @"type": @"module", @"persistent": @YES } };
 
 TEST(WKWebExtensionAPIWebRequest, EventListenerTest)
 {