1 files changed, 706 insertions, 0 deletions
diff --git a/dom/html/HTMLLinkElement.cpp b/dom/html/HTMLLinkElement.cpp
new file mode 100644
index 0000000000..53c2d86d8d
--- /dev/null
+++ b/dom/html/HTMLLinkElement.cpp
@@ -0,0 +1,706 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/HTMLLinkElement.h"
+
+#include "mozilla/AsyncEventDispatcher.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Components.h"
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StaticPrefs_network.h"
+#include "mozilla/dom/BindContext.h"
+#include "mozilla/dom/DocumentInlines.h"
+#include "mozilla/dom/HTMLLinkElementBinding.h"
+#include "mozilla/dom/HTMLDNSPrefetch.h"
+#include "mozilla/dom/ReferrerInfo.h"
+#include "mozilla/dom/ScriptLoader.h"
+#include "nsContentUtils.h"
+#include "nsDOMTokenList.h"
+#include "nsGenericHTMLElement.h"
+#include "nsGkAtoms.h"
+#include "nsIContentInlines.h"
+#include "mozilla/dom/Document.h"
+#include "nsINode.h"
+#include "nsIPrefetchService.h"
+#include "nsISizeOf.h"
+#include "nsPIDOMWindow.h"
+#include "nsReadableUtils.h"
+#include "nsStyleConsts.h"
+#include "nsUnicharUtils.h"
+#include "nsWindowSizes.h"
+#include "nsIContentPolicy.h"
+#include "nsMimeTypes.h"
+#include "imgLoader.h"
+#include "MediaContainerType.h"
+#include "DecoderDoctorDiagnostics.h"
+#include "DecoderTraits.h"
+#include "MediaList.h"
+#include "nsAttrValueInlines.h"
+
+NS_IMPL_NS_NEW_HTML_ELEMENT(Link)
+
+namespace mozilla::dom {
+
+HTMLLinkElement::HTMLLinkElement(
+    already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo)
+    : nsGenericHTMLElement(std::move(aNodeInfo)) {}
+
+HTMLLinkElement::~HTMLLinkElement() { SupportsDNSPrefetch::Destroyed(*this); }
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(HTMLLinkElement)
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(HTMLLinkElement,
+                                                  nsGenericHTMLElement)
+  tmp->LinkStyle::Traverse(cb);
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mRelList)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mSizes)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mBlocking)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(HTMLLinkElement,
+                                                nsGenericHTMLElement)
+  tmp->LinkStyle::Unlink();
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mRelList)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mSizes)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mBlocking)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED_0(HTMLLinkElement,
+                                               nsGenericHTMLElement)
+
+NS_IMPL_ELEMENT_CLONE(HTMLLinkElement)
+
+bool HTMLLinkElement::Disabled() const {
+  return GetBoolAttr(nsGkAtoms::disabled);
+}
+
+void HTMLLinkElement::SetDisabled(bool aDisabled, ErrorResult& aRv) {
+  return SetHTMLBoolAttr(nsGkAtoms::disabled, aDisabled, aRv);
+}
+
+nsresult HTMLLinkElement::BindToTree(BindContext& aContext, nsINode& aParent) {
+  nsresult rv = nsGenericHTMLElement::BindToTree(aContext, aParent);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (IsInComposedDoc()) {
+    TryDNSPrefetchOrPreconnectOrPrefetchOrPreloadOrPrerender();
+  }
+
+  LinkStyle::BindToTree();
+
+  if (IsInUncomposedDoc()) {
+    if (AttrValueIs(kNameSpaceID_None, nsGkAtoms::rel, nsGkAtoms::localization,
+                    eIgnoreCase)) {
+      aContext.OwnerDoc().LocalizationLinkAdded(this);
+    }
+
+    LinkAdded();
+  }
+
+  return rv;
+}
+
+void HTMLLinkElement::LinkAdded() {
+  CreateAndDispatchEvent(u"DOMLinkAdded"_ns);
+}
+
+void HTMLLinkElement::UnbindFromTree(bool aNullParent) {
+  CancelDNSPrefetch(*this);
+  CancelPrefetchOrPreload();
+
+  // If this is reinserted back into the document it will not be
+  // from the parser.
+  Document* oldDoc = GetUncomposedDoc();
+  ShadowRoot* oldShadowRoot = GetContainingShadow();
+
+  // We want to update the localization but only if the link is removed from a
+  // DOM change, and not because the document is going away.
+  bool ignore;
+  if (oldDoc) {
+    if (oldDoc->GetScriptHandlingObject(ignore) &&
+        AttrValueIs(kNameSpaceID_None, nsGkAtoms::rel, nsGkAtoms::localization,
+                    eIgnoreCase)) {
+      oldDoc->LocalizationLinkRemoved(this);
+    }
+  }
+
+  nsGenericHTMLElement::UnbindFromTree(aNullParent);
+
+  Unused << UpdateStyleSheetInternal(oldDoc, oldShadowRoot);
+}
+
+bool HTMLLinkElement::ParseAttribute(int32_t aNamespaceID, nsAtom* aAttribute,
+                                     const nsAString& aValue,
+                                     nsIPrincipal* aMaybeScriptedPrincipal,
+                                     nsAttrValue& aResult) {
+  if (aNamespaceID == kNameSpaceID_None) {
+    if (aAttribute == nsGkAtoms::crossorigin) {
+      ParseCORSValue(aValue, aResult);
+      return true;
+    }
+
+    if (aAttribute == nsGkAtoms::as) {
+      net::ParseAsValue(aValue, aResult);
+      return true;
+    }
+
+    if (aAttribute == nsGkAtoms::sizes) {
+      aResult.ParseAtomArray(aValue);
+      return true;
+    }
+
+    if (aAttribute == nsGkAtoms::integrity) {
+      aResult.ParseStringOrAtom(aValue);
+      return true;
+    }
+
+    if (aAttribute == nsGkAtoms::fetchpriority) {
+      ParseFetchPriority(aValue, aResult);
+      return true;
+    }
+  }
+
+  return nsGenericHTMLElement::ParseAttribute(aNamespaceID, aAttribute, aValue,
+                                              aMaybeScriptedPrincipal, aResult);
+}
+
+void HTMLLinkElement::CreateAndDispatchEvent(const nsAString& aEventName) {
+  MOZ_ASSERT(IsInUncomposedDoc());
+
+  // In the unlikely case that both rev is specified *and* rel=stylesheet,
+  // this code will cause the event to fire, on the principle that maybe the
+  // page really does want to specify that its author is a stylesheet. Since
+  // this should never actually happen and the performance hit is minimal,
+  // doing the "right" thing costs virtually nothing here, even if it doesn't
+  // make much sense.
+  static AttrArray::AttrValuesArray strings[] = {
+      nsGkAtoms::_empty, nsGkAtoms::stylesheet, nullptr};
+
+  if (!nsContentUtils::HasNonEmptyAttr(this, kNameSpaceID_None,
+                                       nsGkAtoms::rev) &&
+      FindAttrValueIn(kNameSpaceID_None, nsGkAtoms::rel, strings,
+                      eIgnoreCase) != AttrArray::ATTR_VALUE_NO_MATCH) {
+    return;
+  }
+
+  RefPtr<AsyncEventDispatcher> asyncDispatcher = new AsyncEventDispatcher(
+      this, aEventName, CanBubble::eYes, ChromeOnlyDispatch::eYes);
+  // Always run async in order to avoid running script when the content
+  // sink isn't expecting it.
+  asyncDispatcher->PostDOMEvent();
+}
+
+void HTMLLinkElement::BeforeSetAttr(int32_t aNameSpaceID, nsAtom* aName,
+                                    const nsAttrValue* aValue, bool aNotify) {
+  if (aNameSpaceID == kNameSpaceID_None &&
+      (aName == nsGkAtoms::href || aName == nsGkAtoms::rel)) {
+    CancelDNSPrefetch(*this);
+    CancelPrefetchOrPreload();
+  }
+
+  return nsGenericHTMLElement::BeforeSetAttr(aNameSpaceID, aName, aValue,
+                                             aNotify);
+}
+
+void HTMLLinkElement::AfterSetAttr(int32_t aNameSpaceID, nsAtom* aName,
+                                   const nsAttrValue* aValue,
+                                   const nsAttrValue* aOldValue,
+                                   nsIPrincipal* aSubjectPrincipal,
+                                   bool aNotify) {
+  if (aNameSpaceID == kNameSpaceID_None && aName == nsGkAtoms::href) {
+    mCachedURI = nullptr;
+    if (IsInUncomposedDoc()) {
+      CreateAndDispatchEvent(u"DOMLinkChanged"_ns);
+    }
+    mTriggeringPrincipal = nsContentUtils::GetAttrTriggeringPrincipal(
+        this, aValue ? aValue->GetStringValue() : EmptyString(),
+        aSubjectPrincipal);
+
+    // If the link has `rel=localization` and its `href` attribute is changed,
+    // update the list of localization links.
+    if (AttrValueIs(kNameSpaceID_None, nsGkAtoms::rel, nsGkAtoms::localization,
+                    eIgnoreCase)) {
+      if (Document* doc = GetUncomposedDoc()) {
+        if (aOldValue) {
+          doc->LocalizationLinkRemoved(this);
+        }
+        if (aValue) {
+          doc->LocalizationLinkAdded(this);
+        }
+      }
+    }
+  }
+
+  // If a link's `rel` attribute was changed from or to `localization`,
+  // update the list of localization links.
+  if (aNameSpaceID == kNameSpaceID_None && aName == nsGkAtoms::rel) {
+    if (Document* doc = GetUncomposedDoc()) {
+      if ((aValue && aValue->Equals(nsGkAtoms::localization, eIgnoreCase)) &&
+          (!aOldValue ||
+           !aOldValue->Equals(nsGkAtoms::localization, eIgnoreCase))) {
+        doc->LocalizationLinkAdded(this);
+      } else if ((aOldValue &&
+                  aOldValue->Equals(nsGkAtoms::localization, eIgnoreCase)) &&
+                 (!aValue ||
+                  !aValue->Equals(nsGkAtoms::localization, eIgnoreCase))) {
+        doc->LocalizationLinkRemoved(this);
+      }
+    }
+  }
+
+  if (aValue) {
+    if (aNameSpaceID == kNameSpaceID_None &&
+        (aName == nsGkAtoms::href || aName == nsGkAtoms::rel ||
+         aName == nsGkAtoms::title || aName == nsGkAtoms::media ||
+         aName == nsGkAtoms::type || aName == nsGkAtoms::as ||
+         aName == nsGkAtoms::crossorigin || aName == nsGkAtoms::disabled)) {
+      bool dropSheet = false;
+      if (aName == nsGkAtoms::rel) {
+        nsAutoString value;
+        aValue->ToString(value);
+        uint32_t linkTypes = ParseLinkTypes(value);
+        if (GetSheet()) {
+          dropSheet = !(linkTypes & eSTYLESHEET);
+        }
+      }
+
+      if ((aName == nsGkAtoms::rel || aName == nsGkAtoms::href) &&
+          IsInComposedDoc()) {
+        TryDNSPrefetchOrPreconnectOrPrefetchOrPreloadOrPrerender();
+      }
+
+      if ((aName == nsGkAtoms::as || aName == nsGkAtoms::type ||
+           aName == nsGkAtoms::crossorigin || aName == nsGkAtoms::media) &&
+          IsInComposedDoc()) {
+        UpdatePreload(aName, aValue, aOldValue);
+      }
+
+      const bool forceUpdate =
+          dropSheet || aName == nsGkAtoms::title || aName == nsGkAtoms::media ||
+          aName == nsGkAtoms::type || aName == nsGkAtoms::disabled;
+
+      Unused << UpdateStyleSheetInternal(
+          nullptr, nullptr, forceUpdate ? ForceUpdate::Yes : ForceUpdate::No);
+    }
+  } else {
+    if (aNameSpaceID == kNameSpaceID_None) {
+      if (aName == nsGkAtoms::disabled) {
+        mExplicitlyEnabled = true;
+      }
+      // Since removing href or rel makes us no longer link to a stylesheet,
+      // force updates for those too.
+      if (aName == nsGkAtoms::href || aName == nsGkAtoms::rel ||
+          aName == nsGkAtoms::title || aName == nsGkAtoms::media ||
+          aName == nsGkAtoms::type || aName == nsGkAtoms::disabled) {
+        Unused << UpdateStyleSheetInternal(nullptr, nullptr, ForceUpdate::Yes);
+      }
+      if ((aName == nsGkAtoms::as || aName == nsGkAtoms::type ||
+           aName == nsGkAtoms::crossorigin || aName == nsGkAtoms::media) &&
+          IsInComposedDoc()) {
+        UpdatePreload(aName, aValue, aOldValue);
+      }
+    }
+  }
+
+  return nsGenericHTMLElement::AfterSetAttr(
+      aNameSpaceID, aName, aValue, aOldValue, aSubjectPrincipal, aNotify);
+}
+
+// Keep this and the arrays below in sync with ToLinkMask in LinkStyle.cpp.
+#define SUPPORTED_REL_VALUES_BASE                                           \
+  "preload", "prefetch", "dns-prefetch", "stylesheet", "next", "alternate", \
+      "preconnect", "icon", "search", nullptr
+
+static const DOMTokenListSupportedToken sSupportedRelValueCombinations[][12] = {
+    {SUPPORTED_REL_VALUES_BASE},
+    {"manifest", SUPPORTED_REL_VALUES_BASE},
+    {"modulepreload", SUPPORTED_REL_VALUES_BASE},
+    {"modulepreload", "manifest", SUPPORTED_REL_VALUES_BASE}};
+#undef SUPPORTED_REL_VALUES_BASE
+
+nsDOMTokenList* HTMLLinkElement::RelList() {
+  if (!mRelList) {
+    int index = (StaticPrefs::dom_manifest_enabled() ? 1 : 0) |
+                (StaticPrefs::network_modulepreload() ? 2 : 0);
+
+    mRelList = new nsDOMTokenList(this, nsGkAtoms::rel,
+                                  sSupportedRelValueCombinations[index]);
+  }
+  return mRelList;
+}
+
+Maybe<LinkStyle::SheetInfo> HTMLLinkElement::GetStyleSheetInfo() {
+  nsAutoString rel;
+  GetAttr(nsGkAtoms::rel, rel);
+  uint32_t linkTypes = ParseLinkTypes(rel);
+  if (!(linkTypes & eSTYLESHEET)) {
+    return Nothing();
+  }
+
+  if (!IsCSSMimeTypeAttributeForLinkElement(*this)) {
+    return Nothing();
+  }
+
+  if (Disabled()) {
+    return Nothing();
+  }
+
+  nsAutoString title;
+  nsAutoString media;
+  GetTitleAndMediaForElement(*this, title, media);
+
+  bool alternate = linkTypes & eALTERNATE;
+  if (alternate && title.IsEmpty()) {
+    // alternates must have title.
+    return Nothing();
+  }
+
+  if (!HasNonEmptyAttr(nsGkAtoms::href)) {
+    return Nothing();
+  }
+
+  nsAutoString integrity;
+  GetAttr(nsGkAtoms::integrity, integrity);
+
+  nsCOMPtr<nsIURI> uri = GetURI();
+  nsCOMPtr<nsIPrincipal> prin = mTriggeringPrincipal;
+
+  nsAutoString nonce;
+  nsString* cspNonce = static_cast<nsString*>(GetProperty(nsGkAtoms::nonce));
+  if (cspNonce) {
+    nonce = *cspNonce;
+  }
+
+  return Some(SheetInfo{
+      *OwnerDoc(),
+      this,
+      uri.forget(),
+      prin.forget(),
+      MakeAndAddRef<ReferrerInfo>(*this),
+      GetCORSMode(),
+      title,
+      media,
+      integrity,
+      nonce,
+      alternate ? HasAlternateRel::Yes : HasAlternateRel::No,
+      IsInline::No,
+      mExplicitlyEnabled ? IsExplicitlyEnabled::Yes : IsExplicitlyEnabled::No,
+      GetFetchPriority(),
+  });
+}
+
+void HTMLLinkElement::AddSizeOfExcludingThis(nsWindowSizes& aSizes,
+                                             size_t* aNodeSize) const {
+  nsGenericHTMLElement::AddSizeOfExcludingThis(aSizes, aNodeSize);
+  if (nsCOMPtr<nsISizeOf> iface = do_QueryInterface(mCachedURI)) {
+    *aNodeSize += iface->SizeOfExcludingThis(aSizes.mState.mMallocSizeOf);
+  }
+}
+
+JSObject* HTMLLinkElement::WrapNode(JSContext* aCx,
+                                    JS::Handle<JSObject*> aGivenProto) {
+  return HTMLLinkElement_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void HTMLLinkElement::GetAs(nsAString& aResult) {
+  GetEnumAttr(nsGkAtoms::as, "", aResult);
+}
+
+void HTMLLinkElement::GetContentPolicyMimeTypeMedia(
+    nsAttrValue& aAsAttr, nsContentPolicyType& aPolicyType, nsString& aMimeType,
+    nsAString& aMedia) {
+  nsAutoString as;
+  GetAttr(nsGkAtoms::as, as);
+  net::ParseAsValue(as, aAsAttr);
+  aPolicyType = net::AsValueToContentPolicy(aAsAttr);
+
+  nsAutoString type;
+  GetAttr(nsGkAtoms::type, type);
+  nsAutoString notUsed;
+  nsContentUtils::SplitMimeType(type, aMimeType, notUsed);
+
+  GetAttr(nsGkAtoms::media, aMedia);
+}
+
+void HTMLLinkElement::
+    TryDNSPrefetchOrPreconnectOrPrefetchOrPreloadOrPrerender() {
+  MOZ_ASSERT(IsInComposedDoc());
+  if (!HasAttr(nsGkAtoms::href)) {
+    return;
+  }
+
+  nsAutoString rel;
+  if (!GetAttr(nsGkAtoms::rel, rel)) {
+    return;
+  }
+
+  if (!nsContentUtils::PrefetchPreloadEnabled(OwnerDoc()->GetDocShell())) {
+    return;
+  }
+
+  uint32_t linkTypes = ParseLinkTypes(rel);
+
+  if ((linkTypes & ePREFETCH) || (linkTypes & eNEXT)) {
+    nsCOMPtr<nsIPrefetchService> prefetchService(
+        components::Prefetch::Service());
+    if (prefetchService) {
+      if (nsCOMPtr<nsIURI> uri = GetURI()) {
+        auto referrerInfo = MakeRefPtr<ReferrerInfo>(*this);
+        prefetchService->PrefetchURI(uri, referrerInfo, this,
+                                     linkTypes & ePREFETCH);
+        return;
+      }
+    }
+  }
+
+  if (linkTypes & ePRELOAD) {
+    if (nsCOMPtr<nsIURI> uri = GetURI()) {
+      nsContentPolicyType policyType;
+
+      nsAttrValue asAttr;
+      nsAutoString mimeType;
+      nsAutoString media;
+      GetContentPolicyMimeTypeMedia(asAttr, policyType, mimeType, media);
+
+      if (policyType == nsIContentPolicy::TYPE_INVALID ||
+          !net::CheckPreloadAttrs(asAttr, mimeType, media, OwnerDoc())) {
+        // Ignore preload with a wrong or empty as attribute.
+        net::WarnIgnoredPreload(*OwnerDoc(), *uri);
+        return;
+      }
+
+      StartPreload(policyType);
+      return;
+    }
+  }
+
+  if (linkTypes & eMODULE_PRELOAD) {
+    ScriptLoader* scriptLoader = OwnerDoc()->ScriptLoader();
+    ModuleLoader* moduleLoader = scriptLoader->GetModuleLoader();
+
+    if (!moduleLoader) {
+      // For the print preview documents, at this moment it doesn't have module
+      // loader yet, as the (print preview) document is not attached to the
+      // nsIDocumentViewer yet, so it doesn't have the GlobalObject.
+      // Also, the script elements won't be processed as they are also cloned
+      // from the original document.
+      // So we simply bail out if the module loader is null.
+      return;
+    }
+
+    if (!StaticPrefs::network_modulepreload()) {
+      // Keep behavior from https://phabricator.services.mozilla.com/D149371,
+      // prior to main implementation of modulepreload
+      moduleLoader->DisallowImportMaps();
+      return;
+    }
+
+    // https://html.spec.whatwg.org/multipage/semantics.html#processing-the-media-attribute
+    // TODO: apply this check for all linkTypes
+    nsAutoString media;
+    if (GetAttr(nsGkAtoms::media, media)) {
+      RefPtr<mozilla::dom::MediaList> mediaList =
+          mozilla::dom::MediaList::Create(NS_ConvertUTF16toUTF8(media));
+      if (!mediaList->Matches(*OwnerDoc())) {
+        return;
+      }
+    }
+
+    // TODO: per spec, apply this check for ePREFETCH as well
+    if (!HasNonEmptyAttr(nsGkAtoms::href)) {
+      return;
+    }
+
+    nsAutoString as;
+    GetAttr(nsGkAtoms::as, as);
+
+    if (!net::IsScriptLikeOrInvalid(as)) {
+      RefPtr<AsyncEventDispatcher> asyncDispatcher = new AsyncEventDispatcher(
+          this, u"error"_ns, CanBubble::eNo, ChromeOnlyDispatch::eNo);
+      asyncDispatcher->PostDOMEvent();
+      return;
+    }
+
+    nsCOMPtr<nsIURI> uri = GetURI();
+    if (!uri) {
+      return;
+    }
+
+    // https://html.spec.whatwg.org/multipage/webappapis.html#fetch-a-modulepreload-module-script-graph
+    // Step 1. Disallow further import maps given settings object.
+    moduleLoader->DisallowImportMaps();
+
+    StartPreload(nsIContentPolicy::TYPE_SCRIPT);
+    return;
+  }
+
+  if (linkTypes & ePRECONNECT) {
+    if (nsCOMPtr<nsIURI> uri = GetURI()) {
+      OwnerDoc()->MaybePreconnect(
+          uri, AttrValueToCORSMode(GetParsedAttr(nsGkAtoms::crossorigin)));
+      return;
+    }
+  }
+
+  if (linkTypes & eDNS_PREFETCH) {
+    TryDNSPrefetch(*this);
+  }
+}
+
+void HTMLLinkElement::UpdatePreload(nsAtom* aName, const nsAttrValue* aValue,
+                                    const nsAttrValue* aOldValue) {
+  MOZ_ASSERT(IsInComposedDoc());
+
+  if (!HasAttr(nsGkAtoms::href)) {
+    return;
+  }
+
+  nsAutoString rel;
+  if (!GetAttr(nsGkAtoms::rel, rel)) {
+    return;
+  }
+
+  if (!nsContentUtils::PrefetchPreloadEnabled(OwnerDoc()->GetDocShell())) {
+    return;
+  }
+
+  uint32_t linkTypes = ParseLinkTypes(rel);
+
+  if (!(linkTypes & ePRELOAD)) {
+    return;
+  }
+
+  nsCOMPtr<nsIURI> uri = GetURI();
+  if (!uri) {
+    return;
+  }
+
+  nsAttrValue asAttr;
+  nsContentPolicyType asPolicyType;
+  nsAutoString mimeType;
+  nsAutoString media;
+  GetContentPolicyMimeTypeMedia(asAttr, asPolicyType, mimeType, media);
+
+  if (asPolicyType == nsIContentPolicy::TYPE_INVALID ||
+      !net::CheckPreloadAttrs(asAttr, mimeType, media, OwnerDoc())) {
+    // Ignore preload with a wrong or empty as attribute, but be sure to cancel
+    // the old one.
+    CancelPrefetchOrPreload();
+    net::WarnIgnoredPreload(*OwnerDoc(), *uri);
+    return;
+  }
+
+  if (aName == nsGkAtoms::crossorigin) {
+    CORSMode corsMode = AttrValueToCORSMode(aValue);
+    CORSMode oldCorsMode = AttrValueToCORSMode(aOldValue);
+    if (corsMode != oldCorsMode) {
+      CancelPrefetchOrPreload();
+      StartPreload(asPolicyType);
+    }
+    return;
+  }
+
+  nsContentPolicyType oldPolicyType;
+
+  if (aName == nsGkAtoms::as) {
+    if (aOldValue) {
+      oldPolicyType = net::AsValueToContentPolicy(*aOldValue);
+      if (!net::CheckPreloadAttrs(*aOldValue, mimeType, media, OwnerDoc())) {
+        oldPolicyType = nsIContentPolicy::TYPE_INVALID;
+      }
+    } else {
+      oldPolicyType = nsIContentPolicy::TYPE_INVALID;
+    }
+  } else if (aName == nsGkAtoms::type) {
+    nsAutoString oldType;
+    nsAutoString notUsed;
+    if (aOldValue) {
+      aOldValue->ToString(oldType);
+    }
+    nsAutoString oldMimeType;
+    nsContentUtils::SplitMimeType(oldType, oldMimeType, notUsed);
+    if (net::CheckPreloadAttrs(asAttr, oldMimeType, media, OwnerDoc())) {
+      oldPolicyType = asPolicyType;
+    } else {
+      oldPolicyType = nsIContentPolicy::TYPE_INVALID;
+    }
+  } else {
+    MOZ_ASSERT(aName == nsGkAtoms::media);
+    nsAutoString oldMedia;
+    if (aOldValue) {
+      aOldValue->ToString(oldMedia);
+    }
+    if (net::CheckPreloadAttrs(asAttr, mimeType, oldMedia, OwnerDoc())) {
+      oldPolicyType = asPolicyType;
+    } else {
+      oldPolicyType = nsIContentPolicy::TYPE_INVALID;
+    }
+  }
+
+  if (asPolicyType != oldPolicyType &&
+      oldPolicyType != nsIContentPolicy::TYPE_INVALID) {
+    CancelPrefetchOrPreload();
+  }
+
+  // Trigger a new preload if the policy type has changed.
+  if (asPolicyType != oldPolicyType) {
+    StartPreload(asPolicyType);
+  }
+}
+
+void HTMLLinkElement::CancelPrefetchOrPreload() {
+  CancelPreload();
+
+  nsCOMPtr<nsIPrefetchService> prefetchService(components::Prefetch::Service());
+  if (prefetchService) {
+    if (nsCOMPtr<nsIURI> uri = GetURI()) {
+      prefetchService->CancelPrefetchPreloadURI(uri, this);
+    }
+  }
+}
+
+void HTMLLinkElement::StartPreload(nsContentPolicyType aPolicyType) {
+  MOZ_ASSERT(!mPreload, "Forgot to cancel the running preload");
+  RefPtr<PreloaderBase> preload =
+      OwnerDoc()->Preloads().PreloadLinkElement(this, aPolicyType);
+  mPreload = preload.get();
+}
+
+void HTMLLinkElement::CancelPreload() {
+  if (mPreload) {
+    // This will cancel the loading channel if this was the last referred node
+    // and the preload is not used up until now to satisfy a regular tag load
+    // request.
+    mPreload->RemoveLinkPreloadNode(this);
+    mPreload = nullptr;
+  }
+}
+
+bool HTMLLinkElement::IsCSSMimeTypeAttributeForLinkElement(
+    const Element& aSelf) {
+  // Processing the type attribute per
+  // https://html.spec.whatwg.org/multipage/semantics.html#processing-the-type-attribute
+  // for HTML link elements.
+  nsAutoString type;
+  nsAutoString mimeType;
+  nsAutoString notUsed;
+  aSelf.GetAttr(nsGkAtoms::type, type);
+  nsContentUtils::SplitMimeType(type, mimeType, notUsed);
+  return mimeType.IsEmpty() || mimeType.LowerCaseEqualsLiteral("text/css");
+}
+
+nsDOMTokenList* HTMLLinkElement::Blocking() {
+  if (!mBlocking) {
+    mBlocking =
+        new nsDOMTokenList(this, nsGkAtoms::blocking, sSupportedBlockingValues);
+  }
+  return mBlocking;
+}
+
+}  // namespace mozilla::dom