Remove reference cycle from WebExtensionAction.

https://webkit.org/b/278800
rdar://134866275

Reviewed by Timothy Hatcher.

This patch removes a reference cycle previously present in
WebExtensionAction. Since actions are stored in a WeakHashMap within
WebExtensionContext where the key is either a WebExtensionWindow or
a WebExtensionTab, and since each action would store a strong reference
to whatever window or tab was used as its key, this forms a reference
cycle. This fix changes the m_tab and m_window instance variables on
WebExtensionAction to be of type std::optional<WeakPtr<..>>. This patch
also contains supporting changes within the class to handle this new
type.

* Source/WebKit/UIProcess/API/Cocoa/WKWebExtensionAction.mm:
(-[WKWebExtensionAction associatedTab]): Take reference to an action's
tab in a RefPtr rather than a raw pointer to prevent it dropping out
while in use.
* Source/WebKit/UIProcess/Extensions/Cocoa/WebExtensionActionCocoa.mm:
(WebKit::WebExtensionAction::tab const): Made method const, moved
implementation to .mm file, updated to handle optional member variable.
(WebKit::WebExtensionAction::window const): Made method const, moved
implementation to .mm file, updated to handle optional member variable.
(WebKit::WebExtensionAction::fallbackAction const): Updated to handle
new type of m_tab (optional<WeakPtr<..>>)
(WebKit::WebExtensionAction::platformMenuItems const): Use tab getter
rather than member variable
* Source/WebKit/UIProcess/Extensions/WebExtensionAction.h:
(WebKit::WebExtensionAction::tab): Deleted (moved implementation to
WebExtensionActionCocoa.mm).
(WebKit::WebExtensionAction::window): Deleted (moved implementation to
WebExtensionActionCocoa.mm).

Canonical link: https://commits.webkit.org/283143@main

Source/WebKit/UIProcess/API/Cocoa/WKWebExtensionAction.mm

@@ -72,7 +72,7 @@ - (WKWebExtensionContext *)webExtensionContext
 
 - (id<WKWebExtensionTab>)associatedTab
 {
-    if (auto *tab = _webExtensionAction->tab())
+    if (RefPtr tab = _webExtensionAction->tab())
         return tab->delegate();
     return nil;
 }

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

@@ -589,6 +589,20 @@ - (void)_otherPopoverWillShow:(NSNotification *)notification
     return m_extensionContext.get();
 }
 
+RefPtr<WebExtensionTab> WebExtensionAction::tab() const
+{
+    return m_tab.and_then([](auto const& maybeTab) {
+        return std::optional(RefPtr(maybeTab.get()));
+    }).value_or(nullptr);
+}
+
+RefPtr<WebExtensionWindow> WebExtensionAction::window() const
+{
+    return m_window.and_then([](auto const& maybeWindow) {
+        return std::optional(RefPtr(maybeWindow.get()));
+    }).value_or(nullptr);
+}
+
 void WebExtensionAction::clearCustomizations()
 {
     if (!m_customIcons && m_customPopupPath.isNull() && m_customLabel.isNull() && m_customBadgeText.isNull() && !m_customEnabled && !m_blockedResourceCount)
@@ -628,12 +642,12 @@ - (void)_otherPopoverWillShow:(NSNotification *)notification
     if (!extensionContext())
         return nullptr;
 
-    // Tab actions fallback to the window action.
-    if (m_tab)
-        return extensionContext()->getAction(m_tab->window().get()).ptr();
+    // Tab actions whose tab references have not dropped fallback to the window action.
+    if (RefPtr tab = this->tab())
+        return extensionContext()->getAction(tab->window().get()).ptr();
 
-    // Window actions fallback to the default action.
-    if (m_window)
+    // Window actions and tab actions whose tab references have dropped fallback to the default action.
+    if (m_window.has_value() || m_tab.has_value())
         return &extensionContext()->defaultAction();
 
     // Default actions have no fallback.
@@ -1160,9 +1174,11 @@ - (void)_otherPopoverWillShow:(NSNotification *)notification
     if (!extensionContext())
         return @[ ];
 
-    RefPtr tab = m_tab;
-    if (!tab && m_window)
-        tab = m_window->activeTab();
+    RefPtr tab = this->tab();
+    if (!tab) {
+        if (RefPtr window = this->window())
+            tab = window->activeTab();
+    }
 
     WebExtensionMenuItemContextParameters contextParameters;
     contextParameters.types = WebExtensionMenuItemContextType::Action;

Source/WebKit/UIProcess/Extensions/WebExtensionAction.h

@@ -78,8 +78,8 @@ class WebExtensionAction : public API::ObjectImpl<API::Object::Type::WebExtensio
     bool operator==(const WebExtensionAction&) const;
 
     WebExtensionContext* extensionContext() const;
-    WebExtensionTab* tab() { return m_tab.get(); }
-    WebExtensionWindow* window() { return m_window.get(); }
+    RefPtr<WebExtensionTab> tab() const;
+    RefPtr<WebExtensionWindow> window() const;
 
     void clearCustomizations();
     void clearBlockedResourceCount();
@@ -149,8 +149,8 @@ class WebExtensionAction : public API::ObjectImpl<API::Object::Type::WebExtensio
 #endif
 
     WeakPtr<WebExtensionContext> m_extensionContext;
-    RefPtr<WebExtensionTab> m_tab;
-    RefPtr<WebExtensionWindow> m_window;
+    std::optional<WeakPtr<WebExtensionTab>> m_tab;
+    std::optional<WeakPtr<WebExtensionWindow>> m_window;
 
 #if PLATFORM(IOS_FAMILY)
     RetainPtr<_WKWebExtensionActionViewController> m_popupViewController;