Bug 259253

To reproduce, run these 3 tests back to back: 1. editing/input/cocoa/autocorrect-on.html 2. editing/pasteboard/paste-blockquote-1.html 3. editing/pasteboard/paste-does-not-fire-promises-while-sanitizing-web-content.html Or more generally, 1. Run a test that installs the fake text checker on iOS. 2. Run any other layout test. 3. Run a layout test that shows an edit menu by tapping or selecting text. ...the test in (3) will crash with an overelease under something like: ``` Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0 libobjc.A.dylib 0x1044e2280 objc_release + 16 1 WebKit 0x10d12abac WTF::RetainPtr<UITextChecker>::~RetainPtr() + 8 (RetainPtr.h:198) [inlined] 2 WebKit 0x10d12abac WTF::RetainPtr<UITextChecker>::~RetainPtr() + 8 (RetainPtr.h:196) [inlined] … 10 WebKit 0x10d1226f8 WTF::HashMap<long long, WTF::RetainPtr<UITextChecker>, WTF::DefaultHash<long long>, WTF::HashTraits<long long>, WTF::HashTraits<WTF::RetainPtr<UITextChecker>>, WTF::HashTableTraits>::remove(long long const&) + 80 (HashMap.h:502) [inlined] 11 WebKit 0x10d1226f8 WebKit::TextChecker::closeSpellDocumentWithTag(long long) + 112 (TextCheckerIOS.mm:189) 12 WebKit 0x10d207594 WebKit::WebPageProxy::~WebPageProxy() + 264 (WebPageProxy.cpp:726) 13 WebKit 0x10ce7680c -[WKObject dealloc] + 64 (WKObject.mm:58) ```