LibWeb: Remove `AbortSignal::follow()`

This no longer has any callers.
`AbortSignal::create_dependent_abort_signal()` should be used instead.

Userland/Libraries/LibWeb/DOM/AbortSignal.cpp

@@ -108,29 +108,6 @@ void AbortSignal::visit_edges(JS::Cell::Visitor& visitor)
         visitor.visit(dependent_signal);
 }
 
-// https://dom.spec.whatwg.org/#abortsignal-follow
-void AbortSignal::follow(JS::NonnullGCPtr<AbortSignal> parent_signal)
-{
-    // A followingSignal (an AbortSignal) is made to follow a parentSignal (an AbortSignal) by running these steps:
-
-    // 1. If followingSignal is aborted, then return.
-    if (aborted())
-        return;
-
-    // 2. If parentSignal is aborted, then signal abort on followingSignal with parentSignal’s abort reason.
-    if (parent_signal->aborted()) {
-        signal_abort(parent_signal->reason());
-        return;
-    }
-
-    // 3. Otherwise, add the following abort steps to parentSignal:
-    // NOTE: `this` and `parent_signal` are protected by AbortSignal using JS::SafeFunction.
-    parent_signal->add_abort_algorithm([this, parent_signal] {
-        // 1. Signal abort on followingSignal with parentSignal’s abort reason.
-        signal_abort(parent_signal->reason());
-    });
-}
-
 // https://dom.spec.whatwg.org/#dom-abortsignal-abort
 WebIDL::ExceptionOr<JS::NonnullGCPtr<AbortSignal>> AbortSignal::abort(JS::VM& vm, JS::Value reason)
 {

Userland/Libraries/LibWeb/DOM/AbortSignal.h

@@ -43,8 +43,6 @@ public:
 
     JS::ThrowCompletionOr<void> throw_if_aborted() const;
 
-    void follow(JS::NonnullGCPtr<AbortSignal> parent_signal);
-
     static WebIDL::ExceptionOr<JS::NonnullGCPtr<AbortSignal>> abort(JS::VM&, JS::Value reason);
     static WebIDL::ExceptionOr<JS::NonnullGCPtr<AbortSignal>> timeout(JS::VM&, Web::WebIDL::UnsignedLongLong milliseconds);
     static WebIDL::ExceptionOr<JS::NonnullGCPtr<AbortSignal>> any(JS::VM&, JS::Value signals);