Bug 1855427: The DOMLinkRemoved chrome event is not used anywhere. r=emilio

The event isn't dispatched correctly for DOM manipulations anymore. It is
dispatched when swapping docshells but we don't actually use this event anywhere
except tests so we might as well just remove it entirely.

Differential Revision: https://phabricator.services.mozilla.com/D192333

docshell/test/chrome/bug113934_window.xhtml

@@ -85,7 +85,6 @@
       // which are a result of swapping the docshells.
       var DOMLinkListener = {
         _afterFirst: false,
-        _removedDispatched: false,
         _addedDispatched: false,
         async handleEvent(aEvent) {
           if (!this._afterFirst) {
@@ -134,16 +133,10 @@
             is(this._addedDispatched, false);
             this._addedDispatched = true;
           }
-          else {
-            is(this._removedDispatched, false);
-            this._removedDispatched = true;
-          }
 
-          if (this._addedDispatched && this._removedDispatched) {
+          if (this._addedDispatched) {
             $("f1").removeEventListener("DOMLinkAdded", this);
-            $("f1").removeEventListener("DOMLinkRemoved", this);
             $("f3").removeEventListener("DOMLinkAdded", this);
-            $("f3").removeEventListener("DOMLinkRemoved", this);
             window.close();
             SimpleTest.finish();
           }
@@ -151,9 +144,7 @@
       };
 
       $("f1").addEventListener("DOMLinkAdded", DOMLinkListener);
-      $("f1").addEventListener("DOMLinkRemoved", DOMLinkListener);
       $("f3").addEventListener("DOMLinkAdded", DOMLinkListener);
-      $("f3").addEventListener("DOMLinkRemoved", DOMLinkListener);
 
       var linkElement = $("f1").contentDocument.createElement("link");
       linkElement.setAttribute("rel", "alternate");

dom/base/Document.cpp

@@ -11827,19 +11827,6 @@ void Document::OnPageHide(bool aPersisted, EventTarget* aDispatchStartTarget,
       inFrameLoaderSwap ==
       (mDocumentContainer && mDocumentContainer->InFrameSwap()));
 
-  // Send out notifications that our <link> elements are detached,
-  // but only if this is not a full unload.
-  Element* root = GetRootElement();
-  if (aPersisted && root) {
-    RefPtr<nsContentList> links =
-        NS_GetContentList(root, kNameSpaceID_XHTML, u"link"_ns);
-
-    uint32_t linkCount = links->Length(true);
-    for (uint32_t i = 0; i < linkCount; ++i) {
-      static_cast<HTMLLinkElement*>(links->Item(i, false))->LinkRemoved();
-    }
-  }
-
   if (mAnimationController) {
     mAnimationController->OnPageHide();
   }

dom/html/HTMLLinkElement.cpp

@@ -108,10 +108,6 @@ void HTMLLinkElement::LinkAdded() {
   CreateAndDispatchEvent(u"DOMLinkAdded"_ns);
 }
 
-void HTMLLinkElement::LinkRemoved() {
-  CreateAndDispatchEvent(u"DOMLinkRemoved"_ns);
-}
-
 void HTMLLinkElement::UnbindFromTree(bool aNullParent) {
   CancelDNSPrefetch(*this);
   CancelPrefetchOrPreload();
@@ -130,8 +126,6 @@ void HTMLLinkElement::UnbindFromTree(bool aNullParent) {
                     eIgnoreCase)) {
       oldDoc->LocalizationLinkRemoved(this);
     }
-
-    CreateAndDispatchEvent(u"DOMLinkRemoved"_ns);
   }
 
   nsGenericHTMLElement::UnbindFromTree(aNullParent);

dom/html/HTMLLinkElement.h

@@ -40,7 +40,6 @@ class HTMLLinkElement final : public nsGenericHTMLElement,
   NS_DECL_ADDSIZEOFEXCLUDINGTHIS
 
   void LinkAdded();
-  void LinkRemoved();
 
   // nsINode
   nsresult Clone(dom::NodeInfo*, nsINode** aResult) const override;