Revert [257736@main] Mitigate crashes when removing KVO from NSWindow…

… in -[WKWindowVisibilityObserver stopObserving:]

https://bugs.webkit.org/show_bug.cgi?id=249103
rdar://102360839

Unreviewed revert
This reverts because the new test addition landed as a consistent crash.

* Source/WebKit/UIProcess/mac/WebViewImpl.mm:
(-[WKWindowVisibilityObserver startObserving:]):
(-[WKWindowVisibilityObserver stopObserving:]):
* Tools/TestWebKitAPI/Tests/WebKitCocoa/PrepareForMoveToWindow.mm:

Canonical link: https://commits.webkit.org/257848@main

Source/WebKit/UIProcess/mac/WebViewImpl.mm

@@ -332,10 +332,6 @@ - (void)startObserving:(NSWindow *)window
     if (_shouldObserveFontPanel)
         [self startObservingFontPanel];
 
-    if (objc_getAssociatedObject(window, _impl))
-        return;
-
-    objc_setAssociatedObject(window, _impl, @YES, OBJC_ASSOCIATION_COPY_NONATOMIC);
     [window addObserver:self forKeyPath:@"contentLayoutRect" options:NSKeyValueObservingOptionInitial context:keyValueObservingContext];
     [window addObserver:self forKeyPath:@"titlebarAppearsTransparent" options:NSKeyValueObservingOptionInitial context:keyValueObservingContext];
 }
@@ -366,10 +362,6 @@ - (void)stopObserving:(NSWindow *)window
     if (_shouldObserveFontPanel)
         [[NSFontPanel sharedFontPanel] removeObserver:self forKeyPath:@"visible" context:keyValueObservingContext];
 
-    if (!objc_getAssociatedObject(window, _impl))
-        return;
-
-    objc_setAssociatedObject(window, _impl, nil, OBJC_ASSOCIATION_COPY_NONATOMIC);
     [window removeObserver:self forKeyPath:@"contentLayoutRect" context:keyValueObservingContext];
     [window removeObserver:self forKeyPath:@"titlebarAppearsTransparent" context:keyValueObservingContext];
 }

Tools/TestWebKitAPI/Tests/WebKitCocoa/PrepareForMoveToWindow.mm

@@ -70,23 +70,6 @@
     TestWebKitAPI::Util::run(&done);
 }
 
-TEST(WKWebView, PrepareForMoveToWindowShouldNotCrashWhenRemovingWindowObservers)
-{
-    auto window = adoptNS([NSWindow new]);
-    auto webView = adoptNS([[WKWebView alloc] initWithFrame:NSMakeRect(0, 0, 800, 600)]);
-    [webView synchronouslyLoadTestPageNamed:@"simple"];
-
-    [[window contentView] addSubview:webView.get()];
-    [webView _prepareForMoveToWindow:nil completionHandler:^{ }];
-    [webView _prepareForMoveToWindow:window.get() completionHandler:^{ }];
-
-    __block bool done = false;
-    [webView _prepareForMoveToWindow:nil completionHandler:^{
-        done = true;
-    }];
-    TestWebKitAPI::Util::run(&done);
-}
-
 TEST(WKWebView, PrepareForMoveToWindowThenClose)
 {
     auto webView = adoptNS([[WKWebView alloc] init]);