Add setting for WebKit process management

https://bugs.webkit.org/show_bug.cgi?id=265337
rdar://118789596

Reviewed by Brent Fulgham.

Add setting to manage WebKit processes as extensions. This setting is not enabled by default.

* Source/WTF/Scripts/Preferences/UnifiedWebPreferences.yaml:
* Source/WebKit/UIProcess/AuxiliaryProcessProxy.cpp:
* Source/WebKit/UIProcess/Cocoa/WebProcessPoolCocoa.mm:
(WebKit::WebProcessPool::platformInitialize):
* Source/WebKit/WebProcess/WebPage/WebPage.cpp:

Canonical link: https://commits.webkit.org/271181@main

Source/WTF/Scripts/Preferences/UnifiedWebPreferences.yaml

@@ -3984,6 +3984,18 @@ ManageCaptureStatusBarInGPUProcessEnabled:
     WebCore:
       default: false
 
+ManageWebKitProcessesAsExtensions:
+  type: bool
+  status: internal
+  humanReadableName: "Manage WebKit processes as extensions"
+  humanReadableDescription: "Manage WebKit processes as extensions"
+  condition: USE(EXTENSIONKIT)
+  webcoreBinding: none
+  exposed: [ WebKit ]
+  defaultValue:
+    WebKit:
+      default: false
+
 ManagedMediaSourceEnabled:
   type: bool
   status: stable

Source/WebKit/UIProcess/Cocoa/WebProcessPoolCocoa.mm

@@ -304,11 +304,6 @@ static void logProcessPoolState(const WebProcessPool& pool)
         for (const auto& pool : WebProcessPool::allProcessPools())
             logProcessPoolState(pool.get());
     });
-
-#if USE(EXTENSIONKIT)
-    bool manageProcessesAsExtensions = !CFPreferencesGetAppBooleanValue(CFSTR("disableProcessesAsExtensions"), kCFPreferencesCurrentApplication, nullptr);
-    AuxiliaryProcessProxy::setManageProcessesAsExtensions(manageProcessesAsExtensions);
-#endif
 }
 
 void WebProcessPool::platformResolvePathsForSandboxExtensions()

Source/WebKit/UIProcess/WebProcessPool.cpp

@@ -1105,6 +1105,11 @@ Ref<WebPageProxy> WebProcessPool::createWebPage(PageClient& pageClient, Ref<API:
         pageConfiguration->setWebsiteDataStore(WebKit::WebsiteDataStore::defaultDataStore());
     }
 
+#if USE(EXTENSIONKIT)
+    auto manageWebKitProcessesAsExtensions = pageConfiguration->preferences()->store().getBoolValueForKey(WebPreferencesKey::manageWebKitProcessesAsExtensionsKey());
+    AuxiliaryProcessProxy::setManageProcessesAsExtensions(manageWebKitProcessesAsExtensions);
+#endif
+
     RefPtr<WebProcessProxy> process;
     auto lockdownMode = pageConfiguration->lockdownModeEnabled() ? WebProcessProxy::LockdownMode::Enabled : WebProcessProxy::LockdownMode::Disabled;
     RefPtr relatedPage = pageConfiguration->relatedPage();