Issue 56451: cross_fuzz: Deleted elements lingering in Document::m_elementsById

@ap filed in webkit land-
https://bugs.webkit.org/show_bug.cgi?id=46222

@ap got a checkConsistency() assertion failure with cross_fuzz. This likely means an exploitable security issue, as he has seen in the past.

#0    0x1024820e9 in WTF::ValueCheck<WebCore::AtomicStringImpl*>::checkConsistency at ValueCheck.h:45
#1    0x102602c65 in WTF::HashTable<WebCore::AtomicStringImpl*, std::pair<WebCore::AtomicStringImpl*, WebCore::Element*>, WTF::PairFirstExtractor<std::pair<WebCore::AtomicStringImpl*, WebCore::Element*> >, WTF::PtrHash<WebCore::AtomicStringImpl*>, WTF::PairHashTraits<WTF::HashTraits<WebCore::AtomicStringImpl*>, WTF::HashTraits<WebCore::Element*> >, WTF::HashTraits<WebCore::AtomicStringImpl*> >::checkTableConsistencyExceptSize at HashTable.h:1025
#2    0x102602dd1 in WTF::HashTable<WebCore::AtomicStringImpl*, std::pair<WebCore::AtomicStringImpl*, WebCore::Element*>, WTF::PairFirstExtractor<std::pair<WebCore::AtomicStringImpl*, WebCore::Element*> >, WTF::PtrHash<WebCore::AtomicStringImpl*>, WTF::PairHashTraits<WTF::HashTraits<WebCore::AtomicStringImpl*>, WTF::HashTraits<WebCore::Element*> >, WTF::HashTraits<WebCore::AtomicStringImpl*> >::checkTableConsistency at HashTable.h:998
#3    0x102602e85 in WTF::HashMap<WebCore::AtomicStringImpl*, WebCore::Element*, WTF::PtrHash<WebCore::AtomicStringImpl*>, WTF::HashTraits<WebCore::AtomicStringImpl*>, WTF::HashTraits<WebCore::Element*> >::checkConsistency at HashMap.h:319
#4    0x1025da6f6 in WebCore::Document::getElementById at Document.cpp:909
#5    0x1025da8d2 in WebCore::Document::findAnchor at Document.cpp:4849
#6    0x102737f5f in WebCore::FrameView::scrollToAnchor at FrameView.cpp:970
#7    0x1027382b8 in WebCore::FrameView::scrollToFragment at FrameView.cpp:949
#8    0x102724a2e in WebCore::FrameLoader::loadInSameDocument at FrameLoader.cpp:1657
#9    0x102724cd4 in WebCore::FrameLoader::continueFragmentScrollAfterNavigationPolicy at FrameLoader.cpp:3337
#10    0x102724d0c in WebCore::FrameLoader::callContinueFragmentScrollAfterNavigationPolicy at FrameLoader.cpp:3326
#11    0x102b78d63 in WebCore::PolicyCallback::call at PolicyCallback.cpp:101
#12    0x102b798b3 in WebCore::PolicyChecker::continueAfterNavigationPolicy at PolicyChecker.cpp:160
#13    0x101ea63db in WebFrameLoaderClient::receivedPolicyDecison at WebFrameLoaderClient.mm:1271
#14    0x101ea6470 in -[WebFramePolicyListener receivedPolicyDecision:] at WebFrameLoaderClient.mm:1864
...