Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1380 insertions, 0 deletions

diff --git a/dom/html/HTMLImageElement.cpp b/dom/html/HTMLImageElement.cpp
new file mode 100644
index 0000000000..1aa23cdea8
--- /dev/null
+++ b/dom/html/HTMLImageElement.cpp
@@ -0,0 +1,1380 @@
+/* -*- 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/HTMLImageElement.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/dom/BindContext.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/HTMLImageElementBinding.h"
+#include "mozilla/dom/NameSpaceConstants.h"
+#include "nsGenericHTMLElement.h"
+#include "nsGkAtoms.h"
+#include "nsStyleConsts.h"
+#include "nsPresContext.h"
+#include "nsSize.h"
+#include "mozilla/dom/Document.h"
+#include "nsImageFrame.h"
+#include "nsIScriptContext.h"
+#include "nsContentUtils.h"
+#include "nsContainerFrame.h"
+#include "nsNodeInfoManager.h"
+#include "mozilla/MouseEvents.h"
+#include "nsContentPolicyUtils.h"
+#include "nsFocusManager.h"
+#include "mozilla/dom/DOMIntersectionObserver.h"
+#include "mozilla/dom/HTMLFormElement.h"
+#include "mozilla/dom/MutationEventBinding.h"
+#include "mozilla/dom/UserActivation.h"
+#include "nsAttrValueOrString.h"
+#include "imgLoader.h"
+#include "Image.h"
+
+// Responsive images!
+#include "mozilla/dom/HTMLSourceElement.h"
+#include "mozilla/dom/ResponsiveImageSelector.h"
+
+#include "imgINotificationObserver.h"
+#include "imgRequestProxy.h"
+
+#include "mozilla/CycleCollectedJSContext.h"
+
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/MappedDeclarationsBuilder.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/RestyleManager.h"
+
+#include "nsLayoutUtils.h"
+
+using namespace mozilla::net;
+using mozilla::Maybe;
+
+NS_IMPL_NS_NEW_HTML_ELEMENT(Image)
+
+#ifdef DEBUG
+// Is aSubject a previous sibling of aNode.
+static bool IsPreviousSibling(const nsINode* aSubject, const nsINode* aNode) {
+  if (aSubject == aNode) {
+    return false;
+  }
+
+  nsINode* parent = aSubject->GetParentNode();
+  if (parent && parent == aNode->GetParentNode()) {
+    const Maybe<uint32_t> indexOfSubject = parent->ComputeIndexOf(aSubject);
+    const Maybe<uint32_t> indexOfNode = parent->ComputeIndexOf(aNode);
+    if (MOZ_LIKELY(indexOfSubject.isSome() && indexOfNode.isSome())) {
+      return *indexOfSubject < *indexOfNode;
+    }
+    // XXX Keep the odd traditional behavior for now.
+    return indexOfSubject.isNothing() && indexOfNode.isSome();
+  }
+
+  return false;
+}
+#endif
+
+namespace mozilla::dom {
+
+// Calls LoadSelectedImage on host element unless it has been superseded or
+// canceled -- this is the synchronous section of "update the image data".
+// https://html.spec.whatwg.org/multipage/embedded-content.html#update-the-image-data
+class ImageLoadTask final : public MicroTaskRunnable {
+ public:
+  ImageLoadTask(HTMLImageElement* aElement, bool aAlwaysLoad,
+                bool aUseUrgentStartForChannel)
+      : mElement(aElement),
+        mAlwaysLoad(aAlwaysLoad),
+        mUseUrgentStartForChannel(aUseUrgentStartForChannel) {
+    mDocument = aElement->OwnerDoc();
+    mDocument->BlockOnload();
+  }
+
+  void Run(AutoSlowOperation& aAso) override {
+    if (mElement->mPendingImageLoadTask == this) {
+      mElement->mPendingImageLoadTask = nullptr;
+      mElement->mUseUrgentStartForChannel = mUseUrgentStartForChannel;
+      mElement->LoadSelectedImage(true, true, mAlwaysLoad);
+    }
+    mDocument->UnblockOnload(false);
+  }
+
+  bool Suppressed() override {
+    nsIGlobalObject* global = mElement->GetOwnerGlobal();
+    return global && global->IsInSyncOperation();
+  }
+
+  bool AlwaysLoad() const { return mAlwaysLoad; }
+
+ private:
+  ~ImageLoadTask() = default;
+  RefPtr<HTMLImageElement> mElement;
+  nsCOMPtr<Document> mDocument;
+  bool mAlwaysLoad;
+
+  // True if we want to set nsIClassOfService::UrgentStart to the channel to
+  // get the response ASAP for better user responsiveness.
+  bool mUseUrgentStartForChannel;
+};
+
+HTMLImageElement::HTMLImageElement(
+    already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo)
+    : nsGenericHTMLElement(std::move(aNodeInfo)) {
+  // We start out broken
+  AddStatesSilently(ElementState::BROKEN);
+}
+
+HTMLImageElement::~HTMLImageElement() { nsImageLoadingContent::Destroy(); }
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(HTMLImageElement, nsGenericHTMLElement,
+                                   mResponsiveSelector)
+
+NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED(HTMLImageElement,
+                                             nsGenericHTMLElement,
+                                             nsIImageLoadingContent,
+                                             imgINotificationObserver)
+
+NS_IMPL_ELEMENT_CLONE(HTMLImageElement)
+
+bool HTMLImageElement::IsInteractiveHTMLContent() const {
+  return HasAttr(nsGkAtoms::usemap) ||
+         nsGenericHTMLElement::IsInteractiveHTMLContent();
+}
+
+void HTMLImageElement::AsyncEventRunning(AsyncEventDispatcher* aEvent) {
+  nsImageLoadingContent::AsyncEventRunning(aEvent);
+}
+
+void HTMLImageElement::GetCurrentSrc(nsAString& aValue) {
+  nsCOMPtr<nsIURI> currentURI;
+  GetCurrentURI(getter_AddRefs(currentURI));
+  if (currentURI) {
+    nsAutoCString spec;
+    currentURI->GetSpec(spec);
+    CopyUTF8toUTF16(spec, aValue);
+  } else {
+    SetDOMStringToNull(aValue);
+  }
+}
+
+bool HTMLImageElement::Draggable() const {
+  // images may be dragged unless the draggable attribute is false
+  return !AttrValueIs(kNameSpaceID_None, nsGkAtoms::draggable,
+                      nsGkAtoms::_false, eIgnoreCase);
+}
+
+bool HTMLImageElement::Complete() {
+  // It is still not clear what value should img.complete return in various
+  // cases, see https://github.com/whatwg/html/issues/4884
+
+  if (!HasAttr(nsGkAtoms::srcset) && !HasNonEmptyAttr(nsGkAtoms::src)) {
+    return true;
+  }
+
+  if (!mCurrentRequest || mPendingRequest) {
+    return false;
+  }
+
+  uint32_t status;
+  mCurrentRequest->GetImageStatus(&status);
+  return (status &
+          (imgIRequest::STATUS_LOAD_COMPLETE | imgIRequest::STATUS_ERROR)) != 0;
+}
+
+CSSIntPoint HTMLImageElement::GetXY() {
+  nsIFrame* frame = GetPrimaryFrame(FlushType::Layout);
+  if (!frame) {
+    return CSSIntPoint(0, 0);
+  }
+  return CSSIntPoint::FromAppUnitsRounded(
+      frame->GetOffsetTo(frame->PresShell()->GetRootFrame()));
+}
+
+int32_t HTMLImageElement::X() { return GetXY().x; }
+
+int32_t HTMLImageElement::Y() { return GetXY().y; }
+
+void HTMLImageElement::GetDecoding(nsAString& aValue) {
+  GetEnumAttr(nsGkAtoms::decoding, kDecodingTableDefault->tag, aValue);
+}
+
+already_AddRefed<Promise> HTMLImageElement::Decode(ErrorResult& aRv) {
+  return nsImageLoadingContent::QueueDecodeAsync(aRv);
+}
+
+bool HTMLImageElement::ParseAttribute(int32_t aNamespaceID, nsAtom* aAttribute,
+                                      const nsAString& aValue,
+                                      nsIPrincipal* aMaybeScriptedPrincipal,
+                                      nsAttrValue& aResult) {
+  if (aNamespaceID == kNameSpaceID_None) {
+    if (aAttribute == nsGkAtoms::align) {
+      return ParseAlignValue(aValue, aResult);
+    }
+    if (aAttribute == nsGkAtoms::crossorigin) {
+      ParseCORSValue(aValue, aResult);
+      return true;
+    }
+    if (aAttribute == nsGkAtoms::decoding) {
+      return aResult.ParseEnumValue(aValue, kDecodingTable,
+                                    /* aCaseSensitive = */ false,
+                                    kDecodingTableDefault);
+    }
+    if (aAttribute == nsGkAtoms::loading) {
+      return ParseLoadingAttribute(aValue, aResult);
+    }
+    if (ParseImageAttribute(aAttribute, aValue, aResult)) {
+      return true;
+    }
+  }
+
+  return nsGenericHTMLElement::ParseAttribute(aNamespaceID, aAttribute, aValue,
+                                              aMaybeScriptedPrincipal, aResult);
+}
+
+void HTMLImageElement::MapAttributesIntoRule(
+    MappedDeclarationsBuilder& aBuilder) {
+  MapImageAlignAttributeInto(aBuilder);
+  MapImageBorderAttributeInto(aBuilder);
+  MapImageMarginAttributeInto(aBuilder);
+  MapImageSizeAttributesInto(aBuilder, MapAspectRatio::Yes);
+  MapCommonAttributesInto(aBuilder);
+}
+
+nsChangeHint HTMLImageElement::GetAttributeChangeHint(const nsAtom* aAttribute,
+                                                      int32_t aModType) const {
+  nsChangeHint retval =
+      nsGenericHTMLElement::GetAttributeChangeHint(aAttribute, aModType);
+  if (aAttribute == nsGkAtoms::usemap || aAttribute == nsGkAtoms::ismap) {
+    retval |= nsChangeHint_ReconstructFrame;
+  } else if (aAttribute == nsGkAtoms::alt) {
+    if (aModType == MutationEvent_Binding::ADDITION ||
+        aModType == MutationEvent_Binding::REMOVAL) {
+      retval |= nsChangeHint_ReconstructFrame;
+    }
+  }
+  return retval;
+}
+
+NS_IMETHODIMP_(bool)
+HTMLImageElement::IsAttributeMapped(const nsAtom* aAttribute) const {
+  static const MappedAttributeEntry* const map[] = {
+      sCommonAttributeMap, sImageMarginSizeAttributeMap,
+      sImageBorderAttributeMap, sImageAlignAttributeMap};
+
+  return FindAttributeDependence(aAttribute, map);
+}
+
+nsMapRuleToAttributesFunc HTMLImageElement::GetAttributeMappingFunction()
+    const {
+  return &MapAttributesIntoRule;
+}
+
+void HTMLImageElement::BeforeSetAttr(int32_t aNameSpaceID, nsAtom* aName,
+                                     const nsAttrValue* aValue, bool aNotify) {
+  if (aNameSpaceID == kNameSpaceID_None && mForm &&
+      (aName == nsGkAtoms::name || aName == nsGkAtoms::id)) {
+    // remove the image from the hashtable as needed
+    if (const auto* old = GetParsedAttr(aName); old && !old->IsEmptyString()) {
+      mForm->RemoveImageElementFromTable(
+          this, nsDependentAtomString(old->GetAtomValue()));
+    }
+  }
+
+  return nsGenericHTMLElement::BeforeSetAttr(aNameSpaceID, aName, aValue,
+                                             aNotify);
+}
+
+void HTMLImageElement::AfterSetAttr(int32_t aNameSpaceID, nsAtom* aName,
+                                    const nsAttrValue* aValue,
+                                    const nsAttrValue* aOldValue,
+                                    nsIPrincipal* aMaybeScriptedPrincipal,
+                                    bool aNotify) {
+  if (aNameSpaceID != kNameSpaceID_None) {
+    return nsGenericHTMLElement::AfterSetAttr(aNameSpaceID, aName, aValue,
+                                              aOldValue,
+                                              aMaybeScriptedPrincipal, aNotify);
+  }
+
+  nsAttrValueOrString attrVal(aValue);
+  if (aName == nsGkAtoms::src) {
+    mSrcURI = nullptr;
+    if (aValue && !aValue->IsEmptyString()) {
+      StringToURI(attrVal.String(), OwnerDoc(), getter_AddRefs(mSrcURI));
+    }
+  }
+
+  if (aValue) {
+    AfterMaybeChangeAttr(aNameSpaceID, aName, attrVal, aOldValue,
+                         aMaybeScriptedPrincipal, aNotify);
+  }
+
+  if (mForm && (aName == nsGkAtoms::name || aName == nsGkAtoms::id) && aValue &&
+      !aValue->IsEmptyString()) {
+    // add the image to the hashtable as needed
+    MOZ_ASSERT(aValue->Type() == nsAttrValue::eAtom,
+               "Expected atom value for name/id");
+    mForm->AddImageElementToTable(
+        this, nsDependentAtomString(aValue->GetAtomValue()));
+  }
+
+  bool forceReload = false;
+
+  if (aName == nsGkAtoms::loading && !mLoading) {
+    if (aValue && Loading(aValue->GetEnumValue()) == Loading::Lazy) {
+      SetLazyLoading();
+    } else if (aOldValue &&
+               Loading(aOldValue->GetEnumValue()) == Loading::Lazy) {
+      StopLazyLoading(StartLoading::Yes);
+    }
+  } else if (aName == nsGkAtoms::src && !aValue) {
+    // NOTE: regular src value changes are handled in AfterMaybeChangeAttr, so
+    // this only needs to handle unsetting the src attribute.
+    // Mark channel as urgent-start before load image if the image load is
+    // initaiated by a user interaction.
+    mUseUrgentStartForChannel = UserActivation::IsHandlingUserInput();
+
+    // AfterMaybeChangeAttr handles setting src since it needs to catch
+    // img.src = img.src, so we only need to handle the unset case
+    if (InResponsiveMode()) {
+      if (mResponsiveSelector && mResponsiveSelector->Content() == this) {
+        mResponsiveSelector->SetDefaultSource(VoidString());
+      }
+      UpdateSourceSyncAndQueueImageTask(true);
+    } else {
+      // Bug 1076583 - We still behave synchronously in the non-responsive case
+      CancelImageRequests(aNotify);
+    }
+  } else if (aName == nsGkAtoms::srcset) {
+    // Mark channel as urgent-start before load image if the image load is
+    // initaiated by a user interaction.
+    mUseUrgentStartForChannel = UserActivation::IsHandlingUserInput();
+
+    mSrcsetTriggeringPrincipal = aMaybeScriptedPrincipal;
+
+    PictureSourceSrcsetChanged(this, attrVal.String(), aNotify);
+  } else if (aName == nsGkAtoms::sizes) {
+    // Mark channel as urgent-start before load image if the image load is
+    // initiated by a user interaction.
+    mUseUrgentStartForChannel = UserActivation::IsHandlingUserInput();
+
+    PictureSourceSizesChanged(this, attrVal.String(), aNotify);
+  } else if (aName == nsGkAtoms::decoding) {
+    // Request sync or async image decoding.
+    SetSyncDecodingHint(
+        aValue && static_cast<ImageDecodingType>(aValue->GetEnumValue()) ==
+                      ImageDecodingType::Sync);
+  } else if (aName == nsGkAtoms::referrerpolicy) {
+    ReferrerPolicy referrerPolicy = GetReferrerPolicyAsEnum();
+    // FIXME(emilio): Why only  when not in responsive mode? Also see below for
+    // aNotify.
+    forceReload = aNotify && !InResponsiveMode() &&
+                  referrerPolicy != ReferrerPolicy::_empty &&
+                  referrerPolicy != ReferrerPolicyFromAttr(aOldValue);
+  } else if (aName == nsGkAtoms::crossorigin) {
+    // FIXME(emilio): The aNotify bit seems a bit suspicious, but it is useful
+    // to avoid extra sync loads, specially in non-responsive mode. Ideally we
+    // can unify the responsive and non-responsive code paths (bug 1076583), and
+    // simplify this a bit.
+    forceReload = aNotify && GetCORSMode() != AttrValueToCORSMode(aOldValue);
+  }
+
+  if (forceReload) {
+    // Because we load image synchronously in non-responsive-mode, we need to do
+    // reload after the attribute has been set if the reload is triggered by
+    // cross origin / referrer policy changing.
+    //
+    // Mark channel as urgent-start before load image if the image load is
+    // initiated by a user interaction.
+    mUseUrgentStartForChannel = UserActivation::IsHandlingUserInput();
+    if (InResponsiveMode()) {
+      // Per spec, full selection runs when this changes, even though
+      // it doesn't directly affect the source selection
+      UpdateSourceSyncAndQueueImageTask(true);
+    } else if (ShouldLoadImage()) {
+      // Bug 1076583 - We still use the older synchronous algorithm in
+      // non-responsive mode. Force a new load of the image with the
+      // new cross origin policy
+      ForceReload(aNotify, IgnoreErrors());
+    }
+  }
+
+  return nsGenericHTMLElement::AfterSetAttr(
+      aNameSpaceID, aName, aValue, aOldValue, aMaybeScriptedPrincipal, aNotify);
+}
+
+void HTMLImageElement::OnAttrSetButNotChanged(int32_t aNamespaceID,
+                                              nsAtom* aName,
+                                              const nsAttrValueOrString& aValue,
+                                              bool aNotify) {
+  AfterMaybeChangeAttr(aNamespaceID, aName, aValue, nullptr, nullptr, aNotify);
+  return nsGenericHTMLElement::OnAttrSetButNotChanged(aNamespaceID, aName,
+                                                      aValue, aNotify);
+}
+
+void HTMLImageElement::AfterMaybeChangeAttr(
+    int32_t aNamespaceID, nsAtom* aName, const nsAttrValueOrString& aValue,
+    const nsAttrValue* aOldValue, nsIPrincipal* aMaybeScriptedPrincipal,
+    bool aNotify) {
+  if (aNamespaceID != kNameSpaceID_None || aName != nsGkAtoms::src) {
+    return;
+  }
+
+  // We need to force our image to reload.  This must be done here, not in
+  // AfterSetAttr or BeforeSetAttr, because we want to do it even if the attr is
+  // being set to its existing value, which is normally optimized away as a
+  // no-op.
+  //
+  // If we are in responsive mode, we drop the forced reload behavior,
+  // but still trigger a image load task for img.src = img.src per
+  // spec.
+  //
+  // Both cases handle unsetting src in AfterSetAttr
+  // Mark channel as urgent-start before load image if the image load is
+  // initaiated by a user interaction.
+  mUseUrgentStartForChannel = UserActivation::IsHandlingUserInput();
+
+  mSrcTriggeringPrincipal = nsContentUtils::GetAttrTriggeringPrincipal(
+      this, aValue.String(), aMaybeScriptedPrincipal);
+
+  if (InResponsiveMode()) {
+    if (mResponsiveSelector && mResponsiveSelector->Content() == this) {
+      mResponsiveSelector->SetDefaultSource(mSrcURI, mSrcTriggeringPrincipal);
+    }
+    UpdateSourceSyncAndQueueImageTask(true);
+  } else if (aNotify && ShouldLoadImage()) {
+    // If aNotify is false, we are coming from the parser or some such place;
+    // we'll get bound after all the attributes have been set, so we'll do the
+    // sync image load from BindToTree. Skip the LoadImage call in that case.
+
+    // Note that this sync behavior is partially removed from the spec, bug
+    // 1076583
+
+    // A hack to get animations to reset. See bug 594771.
+    mNewRequestsWillNeedAnimationReset = true;
+
+    // Force image loading here, so that we'll try to load the image from
+    // network if it's set to be not cacheable.
+    // Potentially, false could be passed here rather than aNotify since
+    // UpdateState will be called by SetAttrAndNotify, but there are two
+    // obstacles to this: 1) LoadImage will end up calling
+    // UpdateState(aNotify), and we do not want it to call UpdateState(false)
+    // when aNotify is true, and 2) When this function is called by
+    // OnAttrSetButNotChanged, SetAttrAndNotify will not subsequently call
+    // UpdateState.
+    LoadSelectedImage(/* aForce = */ true, aNotify,
+                      /* aAlwaysLoad = */ true);
+
+    mNewRequestsWillNeedAnimationReset = false;
+  }
+}
+
+void HTMLImageElement::GetEventTargetParent(EventChainPreVisitor& aVisitor) {
+  // We handle image element with attribute ismap in its corresponding frame
+  // element. Set mMultipleActionsPrevented here to prevent the click event
+  // trigger the behaviors in Element::PostHandleEventForLinks
+  WidgetMouseEvent* mouseEvent = aVisitor.mEvent->AsMouseEvent();
+  if (mouseEvent && mouseEvent->IsLeftClickEvent() && IsMap()) {
+    mouseEvent->mFlags.mMultipleActionsPrevented = true;
+  }
+  nsGenericHTMLElement::GetEventTargetParent(aVisitor);
+}
+
+nsINode* HTMLImageElement::GetScopeChainParent() const {
+  if (mForm) {
+    return mForm;
+  }
+  return nsGenericHTMLElement::GetScopeChainParent();
+}
+
+bool HTMLImageElement::IsHTMLFocusable(bool aWithMouse, bool* aIsFocusable,
+                                       int32_t* aTabIndex) {
+  int32_t tabIndex = TabIndex();
+
+  if (IsInComposedDoc() && FindImageMap()) {
+    // Use tab index on individual map areas.
+    *aTabIndex = (sTabFocusModel & eTabFocus_linksMask) ? 0 : -1;
+    // Image map is not focusable itself, but flag as tabbable
+    // so that image map areas get walked into.
+    *aIsFocusable = false;
+    return false;
+  }
+
+  // Can be in tab order if tabindex >=0 and form controls are tabbable.
+  *aTabIndex = (sTabFocusModel & eTabFocus_formElementsMask) ? tabIndex : -1;
+  *aIsFocusable = IsFormControlDefaultFocusable(aWithMouse) &&
+                  (tabIndex >= 0 || GetTabIndexAttrValue().isSome());
+
+  return false;
+}
+
+nsresult HTMLImageElement::BindToTree(BindContext& aContext, nsINode& aParent) {
+  nsresult rv = nsGenericHTMLElement::BindToTree(aContext, aParent);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsImageLoadingContent::BindToTree(aContext, aParent);
+
+  UpdateFormOwner();
+
+  if (HaveSrcsetOrInPicture()) {
+    if (IsInComposedDoc() && !mInDocResponsiveContent) {
+      aContext.OwnerDoc().AddResponsiveContent(this);
+      mInDocResponsiveContent = true;
+    }
+
+    // Mark channel as urgent-start before load image if the image load is
+    // initaiated by a user interaction.
+    mUseUrgentStartForChannel = UserActivation::IsHandlingUserInput();
+
+    // Run selection algorithm when an img element is inserted into a document
+    // in order to react to changes in the environment. See note of
+    // https://html.spec.whatwg.org/multipage/embedded-content.html#img-environment-changes
+    //
+    // We also do this in PictureSourceAdded() if it is in <picture>, so here
+    // we only need to do if its parent is not <picture>, even if there is no
+    // <source>.
+    if (!IsInPicture()) {
+      UpdateSourceSyncAndQueueImageTask(false);
+    }
+  } else if (!InResponsiveMode() && HasAttr(nsGkAtoms::src)) {
+    // We skip loading when our attributes were set from parser land,
+    // so trigger a aForce=false load now to check if things changed.
+    // This isn't necessary for responsive mode, since creating the
+    // image load task is asynchronous we don't need to take special
+    // care to avoid doing so when being filled by the parser.
+
+    // Mark channel as urgent-start before load image if the image load is
+    // initaiated by a user interaction.
+    mUseUrgentStartForChannel = UserActivation::IsHandlingUserInput();
+
+    // We still act synchronously for the non-responsive case (Bug
+    // 1076583), but still need to delay if it is unsafe to run
+    // script.
+
+    // If loading is temporarily disabled, don't even launch MaybeLoadImage.
+    // Otherwise MaybeLoadImage may run later when someone has reenabled
+    // loading.
+    if (LoadingEnabled() && ShouldLoadImage()) {
+      nsContentUtils::AddScriptRunner(
+          NewRunnableMethod<bool>("dom::HTMLImageElement::MaybeLoadImage", this,
+                                  &HTMLImageElement::MaybeLoadImage, false));
+    }
+  }
+
+  return rv;
+}
+
+void HTMLImageElement::UnbindFromTree(bool aNullParent) {
+  if (mForm) {
+    if (aNullParent || !FindAncestorForm(mForm)) {
+      ClearForm(true);
+    } else {
+      UnsetFlags(MAYBE_ORPHAN_FORM_ELEMENT);
+    }
+  }
+
+  if (mInDocResponsiveContent) {
+    OwnerDoc()->RemoveResponsiveContent(this);
+    mInDocResponsiveContent = false;
+  }
+
+  nsImageLoadingContent::UnbindFromTree(aNullParent);
+  nsGenericHTMLElement::UnbindFromTree(aNullParent);
+}
+
+void HTMLImageElement::UpdateFormOwner() {
+  if (!mForm) {
+    mForm = FindAncestorForm();
+  }
+
+  if (mForm && !HasFlag(ADDED_TO_FORM)) {
+    // Now we need to add ourselves to the form
+    nsAutoString nameVal, idVal;
+    GetAttr(nsGkAtoms::name, nameVal);
+    GetAttr(nsGkAtoms::id, idVal);
+
+    SetFlags(ADDED_TO_FORM);
+
+    mForm->AddImageElement(this);
+
+    if (!nameVal.IsEmpty()) {
+      mForm->AddImageElementToTable(this, nameVal);
+    }
+
+    if (!idVal.IsEmpty()) {
+      mForm->AddImageElementToTable(this, idVal);
+    }
+  }
+}
+
+void HTMLImageElement::MaybeLoadImage(bool aAlwaysForceLoad) {
+  // Our base URI may have changed, or we may have had responsive parameters
+  // change while not bound to the tree. However, at this moment, we should have
+  // updated the responsive source in other places, so we don't have to re-parse
+  // src/srcset here. Just need to LoadImage.
+
+  // Note, check LoadingEnabled() after LoadImage call.
+
+  LoadSelectedImage(aAlwaysForceLoad, /* aNotify */ true, aAlwaysForceLoad);
+
+  if (!LoadingEnabled()) {
+    CancelImageRequests(true);
+  }
+}
+
+void HTMLImageElement::NodeInfoChanged(Document* aOldDoc) {
+  nsGenericHTMLElement::NodeInfoChanged(aOldDoc);
+
+  // Reparse the URI if needed. Note that we can't check whether we already have
+  // a parsed URI, because it might be null even if we have a valid src
+  // attribute, if we tried to parse with a different base.
+  mSrcURI = nullptr;
+  nsAutoString src;
+  if (GetAttr(nsGkAtoms::src, src) && !src.IsEmpty()) {
+    StringToURI(src, OwnerDoc(), getter_AddRefs(mSrcURI));
+  }
+
+  if (mLazyLoading) {
+    aOldDoc->GetLazyLoadObserver()->Unobserve(*this);
+    mLazyLoading = false;
+    SetLazyLoading();
+  }
+
+  // Run selection algorithm synchronously when an img element's adopting steps
+  // are run, in order to react to changes in the environment, per spec,
+  // https://html.spec.whatwg.org/multipage/images.html#reacting-to-dom-mutations,
+  // and
+  // https://html.spec.whatwg.org/multipage/images.html#reacting-to-environment-changes.
+  if (InResponsiveMode()) {
+    UpdateResponsiveSource();
+  }
+
+  // Force reload image if adoption steps are run.
+  // If loading is temporarily disabled, don't even launch script runner.
+  // Otherwise script runner may run later when someone has reenabled loading.
+  StartLoadingIfNeeded();
+}
+
+// static
+already_AddRefed<HTMLImageElement> HTMLImageElement::Image(
+    const GlobalObject& aGlobal, const Optional<uint32_t>& aWidth,
+    const Optional<uint32_t>& aHeight, ErrorResult& aError) {
+  nsCOMPtr<nsPIDOMWindowInner> win = do_QueryInterface(aGlobal.GetAsSupports());
+  Document* doc;
+  if (!win || !(doc = win->GetExtantDoc())) {
+    aError.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  RefPtr<mozilla::dom::NodeInfo> nodeInfo = doc->NodeInfoManager()->GetNodeInfo(
+      nsGkAtoms::img, nullptr, kNameSpaceID_XHTML, ELEMENT_NODE);
+
+  auto* nim = nodeInfo->NodeInfoManager();
+  RefPtr<HTMLImageElement> img = new (nim) HTMLImageElement(nodeInfo.forget());
+
+  if (aWidth.WasPassed()) {
+    img->SetWidth(aWidth.Value(), aError);
+    if (aError.Failed()) {
+      return nullptr;
+    }
+
+    if (aHeight.WasPassed()) {
+      img->SetHeight(aHeight.Value(), aError);
+      if (aError.Failed()) {
+        return nullptr;
+      }
+    }
+  }
+
+  return img.forget();
+}
+
+uint32_t HTMLImageElement::Height() { return GetWidthHeightForImage().height; }
+
+uint32_t HTMLImageElement::Width() { return GetWidthHeightForImage().width; }
+
+nsIntSize HTMLImageElement::NaturalSize() {
+  if (!mCurrentRequest) {
+    return {};
+  }
+
+  nsCOMPtr<imgIContainer> image;
+  mCurrentRequest->GetImage(getter_AddRefs(image));
+  if (!image) {
+    return {};
+  }
+
+  nsIntSize size;
+  Unused << image->GetHeight(&size.height);
+  Unused << image->GetWidth(&size.width);
+
+  ImageResolution resolution = image->GetResolution();
+  // NOTE(emilio): What we implement here matches the image-set() spec, but it's
+  // unclear whether this is the right thing to do, see
+  // https://github.com/whatwg/html/pull/5574#issuecomment-826335244.
+  if (mResponsiveSelector) {
+    float density = mResponsiveSelector->GetSelectedImageDensity();
+    MOZ_ASSERT(density >= 0.0);
+    resolution.ScaleBy(density);
+  }
+
+  resolution.ApplyTo(size.width, size.height);
+  return size;
+}
+
+nsresult HTMLImageElement::CopyInnerTo(HTMLImageElement* aDest) {
+  nsresult rv = nsGenericHTMLElement::CopyInnerTo(aDest);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  // In SetAttr (called from nsGenericHTMLElement::CopyInnerTo), aDest skipped
+  // doing the image load because we passed in false for aNotify.  But we
+  // really do want it to do the load, so set it up to happen once the cloning
+  // reaches a stable state.
+  if (!aDest->InResponsiveMode() && aDest->HasAttr(nsGkAtoms::src) &&
+      aDest->ShouldLoadImage()) {
+    // Mark channel as urgent-start before load image if the image load is
+    // initaiated by a user interaction.
+    mUseUrgentStartForChannel = UserActivation::IsHandlingUserInput();
+
+    nsContentUtils::AddScriptRunner(
+        NewRunnableMethod<bool>("dom::HTMLImageElement::MaybeLoadImage", aDest,
+                                &HTMLImageElement::MaybeLoadImage, false));
+  }
+
+  return NS_OK;
+}
+
+CORSMode HTMLImageElement::GetCORSMode() {
+  return AttrValueToCORSMode(GetParsedAttr(nsGkAtoms::crossorigin));
+}
+
+JSObject* HTMLImageElement::WrapNode(JSContext* aCx,
+                                     JS::Handle<JSObject*> aGivenProto) {
+  return HTMLImageElement_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+#ifdef DEBUG
+HTMLFormElement* HTMLImageElement::GetForm() const { return mForm; }
+#endif
+
+void HTMLImageElement::SetForm(HTMLFormElement* aForm) {
+  MOZ_ASSERT(aForm, "Don't pass null here");
+  NS_ASSERTION(!mForm,
+               "We don't support switching from one non-null form to another.");
+
+  mForm = aForm;
+}
+
+void HTMLImageElement::ClearForm(bool aRemoveFromForm) {
+  NS_ASSERTION((mForm != nullptr) == HasFlag(ADDED_TO_FORM),
+               "Form control should have had flag set correctly");
+
+  if (!mForm) {
+    return;
+  }
+
+  if (aRemoveFromForm) {
+    nsAutoString nameVal, idVal;
+    GetAttr(nsGkAtoms::name, nameVal);
+    GetAttr(nsGkAtoms::id, idVal);
+
+    mForm->RemoveImageElement(this);
+
+    if (!nameVal.IsEmpty()) {
+      mForm->RemoveImageElementFromTable(this, nameVal);
+    }
+
+    if (!idVal.IsEmpty()) {
+      mForm->RemoveImageElementFromTable(this, idVal);
+    }
+  }
+
+  UnsetFlags(ADDED_TO_FORM);
+  mForm = nullptr;
+}
+
+void HTMLImageElement::UpdateSourceSyncAndQueueImageTask(
+    bool aAlwaysLoad, const HTMLSourceElement* aSkippedSource) {
+  // Per spec, when updating the image data or reacting to environment
+  // changes, we always run the full selection (including selecting the source
+  // element and the best fit image from srcset) even if it doesn't directly
+  // affect the source selection.
+  //
+  // However, in the spec of updating the image data, the selection of image
+  // source URL is in the asynchronous part (i.e. in a microtask), and so this
+  // doesn't guarantee that the image style is correct after we flush the style
+  // synchornously. So here we update the responsive source synchronously always
+  // to make sure the image source is always up-to-date after each DOM mutation.
+  // Spec issue: https://github.com/whatwg/html/issues/8207.
+  const bool changed = UpdateResponsiveSource(aSkippedSource);
+
+  // If loading is temporarily disabled, we don't want to queue tasks
+  // that may then run when loading is re-enabled.
+  if (!LoadingEnabled() || !ShouldLoadImage()) {
+    return;
+  }
+
+  // Ensure that we don't overwrite a previous load request that requires
+  // a complete load to occur.
+  bool alwaysLoad = aAlwaysLoad;
+  if (mPendingImageLoadTask) {
+    alwaysLoad = alwaysLoad || mPendingImageLoadTask->AlwaysLoad();
+  }
+
+  if (!changed && !alwaysLoad) {
+    return;
+  }
+
+  QueueImageLoadTask(alwaysLoad);
+}
+
+bool HTMLImageElement::HaveSrcsetOrInPicture() {
+  if (HasAttr(nsGkAtoms::srcset)) {
+    return true;
+  }
+
+  return IsInPicture();
+}
+
+bool HTMLImageElement::InResponsiveMode() {
+  // When we lose srcset or leave a <picture> element, the fallback to img.src
+  // will happen from the microtask, and we should behave responsively in the
+  // interim
+  return mResponsiveSelector || mPendingImageLoadTask ||
+         HaveSrcsetOrInPicture();
+}
+
+bool HTMLImageElement::SelectedSourceMatchesLast(nsIURI* aSelectedSource) {
+  // If there was no selected source previously, we don't want to short-circuit
+  // the load. Similarly for if there is no newly selected source.
+  if (!mLastSelectedSource || !aSelectedSource) {
+    return false;
+  }
+  bool equal = false;
+  return NS_SUCCEEDED(mLastSelectedSource->Equals(aSelectedSource, &equal)) &&
+         equal;
+}
+
+nsresult HTMLImageElement::LoadSelectedImage(bool aForce, bool aNotify,
+                                             bool aAlwaysLoad) {
+  // In responsive mode, we have to make sure we ran the full selection algrithm
+  // before loading the selected image.
+  // Use this assertion to catch any cases we missed.
+  MOZ_ASSERT(!UpdateResponsiveSource(),
+             "The image source should be the same because we update the "
+             "responsive source synchronously");
+
+  // The density is default to 1.0 for the src attribute case.
+  double currentDensity = mResponsiveSelector
+                              ? mResponsiveSelector->GetSelectedImageDensity()
+                              : 1.0;
+
+  nsCOMPtr<nsIURI> selectedSource;
+  nsCOMPtr<nsIPrincipal> triggeringPrincipal;
+  ImageLoadType type = eImageLoadType_Normal;
+  bool hasSrc = false;
+  if (mResponsiveSelector) {
+    selectedSource = mResponsiveSelector->GetSelectedImageURL();
+    triggeringPrincipal =
+        mResponsiveSelector->GetSelectedImageTriggeringPrincipal();
+    type = eImageLoadType_Imageset;
+  } else if (mSrcURI || HasAttr(nsGkAtoms::src)) {
+    hasSrc = true;
+    if (mSrcURI) {
+      selectedSource = mSrcURI;
+      if (HaveSrcsetOrInPicture()) {
+        // If we have a srcset attribute or are in a <picture> element, we
+        // always use the Imageset load type, even if we parsed no valid
+        // responsive sources from either, per spec.
+        type = eImageLoadType_Imageset;
+      }
+      triggeringPrincipal = mSrcTriggeringPrincipal;
+    }
+  }
+
+  if (!aAlwaysLoad && SelectedSourceMatchesLast(selectedSource)) {
+    // Update state when only density may have changed (i.e., the source to load
+    // hasn't changed, and we don't do any request at all). We need (apart from
+    // updating our internal state) to tell the image frame because its
+    // intrinsic size may have changed.
+    //
+    // In the case we actually trigger a new load, that load will trigger a call
+    // to nsImageFrame::NotifyNewCurrentRequest, which takes care of that for
+    // us.
+    SetDensity(currentDensity);
+    return NS_OK;
+  }
+
+  // Before we actually defer the lazy-loading
+  if (mLazyLoading) {
+    if (!selectedSource ||
+        !nsContentUtils::IsImageAvailable(this, selectedSource,
+                                          triggeringPrincipal, GetCORSMode())) {
+      return NS_OK;
+    }
+    StopLazyLoading(StartLoading::No);
+  }
+
+  nsresult rv = NS_ERROR_FAILURE;
+
+  // src triggers an error event on invalid URI, unlike other loads.
+  if (selectedSource || hasSrc) {
+    rv = LoadImage(selectedSource, aForce, aNotify, type, triggeringPrincipal);
+  }
+
+  mLastSelectedSource = selectedSource;
+  mCurrentDensity = currentDensity;
+
+  if (NS_FAILED(rv)) {
+    CancelImageRequests(aNotify);
+  }
+  return rv;
+}
+
+void HTMLImageElement::PictureSourceSrcsetChanged(nsIContent* aSourceNode,
+                                                  const nsAString& aNewValue,
+                                                  bool aNotify) {
+  MOZ_ASSERT(aSourceNode == this || IsPreviousSibling(aSourceNode, this),
+             "Should not be getting notifications for non-previous-siblings");
+
+  nsIContent* currentSrc =
+      mResponsiveSelector ? mResponsiveSelector->Content() : nullptr;
+
+  if (aSourceNode == currentSrc) {
+    // We're currently using this node as our responsive selector
+    // source.
+    nsCOMPtr<nsIPrincipal> principal;
+    if (aSourceNode == this) {
+      principal = mSrcsetTriggeringPrincipal;
+    } else if (auto* source = HTMLSourceElement::FromNode(aSourceNode)) {
+      principal = source->GetSrcsetTriggeringPrincipal();
+    }
+    mResponsiveSelector->SetCandidatesFromSourceSet(aNewValue, principal);
+  }
+
+  if (!mInDocResponsiveContent && IsInComposedDoc()) {
+    OwnerDoc()->AddResponsiveContent(this);
+    mInDocResponsiveContent = true;
+  }
+
+  // This always triggers the image update steps per the spec, even if
+  // we are not using this source.
+  UpdateSourceSyncAndQueueImageTask(true);
+}
+
+void HTMLImageElement::PictureSourceSizesChanged(nsIContent* aSourceNode,
+                                                 const nsAString& aNewValue,
+                                                 bool aNotify) {
+  MOZ_ASSERT(aSourceNode == this || IsPreviousSibling(aSourceNode, this),
+             "Should not be getting notifications for non-previous-siblings");
+
+  nsIContent* currentSrc =
+      mResponsiveSelector ? mResponsiveSelector->Content() : nullptr;
+
+  if (aSourceNode == currentSrc) {
+    // We're currently using this node as our responsive selector
+    // source.
+    mResponsiveSelector->SetSizesFromDescriptor(aNewValue);
+  }
+
+  // This always triggers the image update steps per the spec, even if
+  // we are not using this source.
+  UpdateSourceSyncAndQueueImageTask(true);
+}
+
+void HTMLImageElement::PictureSourceMediaOrTypeChanged(nsIContent* aSourceNode,
+                                                       bool aNotify) {
+  MOZ_ASSERT(IsPreviousSibling(aSourceNode, this),
+             "Should not be getting notifications for non-previous-siblings");
+
+  // This always triggers the image update steps per the spec, even if
+  // we are not switching to/from this source
+  UpdateSourceSyncAndQueueImageTask(true);
+}
+
+void HTMLImageElement::PictureSourceDimensionChanged(
+    HTMLSourceElement* aSourceNode, bool aNotify) {
+  MOZ_ASSERT(IsPreviousSibling(aSourceNode, this),
+             "Should not be getting notifications for non-previous-siblings");
+
+  // "width" and "height" affect the dimension of images, but they don't have
+  // impact on the selection of <source> elements. In other words,
+  // UpdateResponsiveSource doesn't change the source, so all we need to do is
+  // just request restyle.
+  if (mResponsiveSelector && mResponsiveSelector->Content() == aSourceNode) {
+    InvalidateAttributeMapping();
+  }
+}
+
+void HTMLImageElement::PictureSourceAdded(HTMLSourceElement* aSourceNode) {
+  MOZ_ASSERT(!aSourceNode || IsPreviousSibling(aSourceNode, this),
+             "Should not be getting notifications for non-previous-siblings");
+
+  UpdateSourceSyncAndQueueImageTask(true);
+}
+
+void HTMLImageElement::PictureSourceRemoved(HTMLSourceElement* aSourceNode) {
+  MOZ_ASSERT(!aSourceNode || IsPreviousSibling(aSourceNode, this),
+             "Should not be getting notifications for non-previous-siblings");
+
+  UpdateSourceSyncAndQueueImageTask(true, aSourceNode);
+}
+
+bool HTMLImageElement::UpdateResponsiveSource(
+    const HTMLSourceElement* aSkippedSource) {
+  bool hadSelector = !!mResponsiveSelector;
+
+  nsIContent* currentSource =
+      mResponsiveSelector ? mResponsiveSelector->Content() : nullptr;
+
+  // Walk source nodes previous to ourselves if IsInPicture().
+  nsINode* candidateSource =
+      IsInPicture() ? GetParentElement()->GetFirstChild() : this;
+
+  // Initialize this as nullptr so we don't have to nullify it when runing out
+  // of siblings without finding ourself, e.g. XBL magic.
+  RefPtr<ResponsiveImageSelector> newResponsiveSelector = nullptr;
+
+  for (; candidateSource; candidateSource = candidateSource->GetNextSibling()) {
+    if (aSkippedSource == candidateSource) {
+      continue;
+    }
+
+    if (candidateSource == currentSource) {
+      // found no better source before current, re-run selection on
+      // that and keep it if it's still usable.
+      bool changed = mResponsiveSelector->SelectImage(true);
+      if (mResponsiveSelector->NumCandidates()) {
+        bool isUsableCandidate = true;
+
+        // an otherwise-usable source element may still have a media query that
+        // may not match any more.
+        if (candidateSource->IsHTMLElement(nsGkAtoms::source) &&
+            !SourceElementMatches(candidateSource->AsElement())) {
+          isUsableCandidate = false;
+        }
+
+        if (isUsableCandidate) {
+          // We are still using the current source, but the selected image may
+          // be changed, so always set the density from the selected image.
+          SetDensity(mResponsiveSelector->GetSelectedImageDensity());
+          return changed;
+        }
+      }
+
+      // no longer valid
+      newResponsiveSelector = nullptr;
+      if (candidateSource == this) {
+        // No further possibilities
+        break;
+      }
+    } else if (candidateSource == this) {
+      // We are the last possible source
+      newResponsiveSelector =
+          TryCreateResponsiveSelector(candidateSource->AsElement());
+      break;
+    } else if (auto* source = HTMLSourceElement::FromNode(candidateSource)) {
+      if (RefPtr<ResponsiveImageSelector> selector =
+              TryCreateResponsiveSelector(source)) {
+        newResponsiveSelector = selector.forget();
+        // This led to a valid source, stop
+        break;
+      }
+    }
+  }
+
+  // If we reach this point, either:
+  // - there was no selector originally, and there is not one now
+  // - there was no selector originally, and there is one now
+  // - there was a selector, and there is a different one now
+  // - there was a selector, and there is not one now
+  SetResponsiveSelector(std::move(newResponsiveSelector));
+  return hadSelector || mResponsiveSelector;
+}
+
+/*static */
+bool HTMLImageElement::SupportedPictureSourceType(const nsAString& aType) {
+  nsAutoString type;
+  nsAutoString params;
+
+  nsContentUtils::SplitMimeType(aType, type, params);
+  if (type.IsEmpty()) {
+    return true;
+  }
+
+  return imgLoader::SupportImageWithMimeType(
+      NS_ConvertUTF16toUTF8(type), AcceptedMimeTypes::IMAGES_AND_DOCUMENTS);
+}
+
+bool HTMLImageElement::SourceElementMatches(Element* aSourceElement) {
+  MOZ_ASSERT(aSourceElement->IsHTMLElement(nsGkAtoms::source));
+
+  MOZ_ASSERT(IsInPicture());
+  MOZ_ASSERT(IsPreviousSibling(aSourceElement, this));
+
+  // Check media and type
+  auto* src = static_cast<HTMLSourceElement*>(aSourceElement);
+  if (!src->MatchesCurrentMedia()) {
+    return false;
+  }
+
+  nsAutoString type;
+  return !src->GetAttr(nsGkAtoms::type, type) ||
+         SupportedPictureSourceType(type);
+}
+
+already_AddRefed<ResponsiveImageSelector>
+HTMLImageElement::TryCreateResponsiveSelector(Element* aSourceElement) {
+  nsCOMPtr<nsIPrincipal> principal;
+
+  // Skip if this is not a <source> with matching media query
+  bool isSourceTag = aSourceElement->IsHTMLElement(nsGkAtoms::source);
+  if (isSourceTag) {
+    if (!SourceElementMatches(aSourceElement)) {
+      return nullptr;
+    }
+    auto* source = HTMLSourceElement::FromNode(aSourceElement);
+    principal = source->GetSrcsetTriggeringPrincipal();
+  } else if (aSourceElement->IsHTMLElement(nsGkAtoms::img)) {
+    // Otherwise this is the <img> tag itself
+    MOZ_ASSERT(aSourceElement == this);
+    principal = mSrcsetTriggeringPrincipal;
+  }
+
+  // Skip if has no srcset or an empty srcset
+  nsString srcset;
+  if (!aSourceElement->GetAttr(nsGkAtoms::srcset, srcset)) {
+    return nullptr;
+  }
+
+  if (srcset.IsEmpty()) {
+    return nullptr;
+  }
+
+  // Try to parse
+  RefPtr<ResponsiveImageSelector> sel =
+      new ResponsiveImageSelector(aSourceElement);
+  if (!sel->SetCandidatesFromSourceSet(srcset, principal)) {
+    // No possible candidates, don't need to bother parsing sizes
+    return nullptr;
+  }
+
+  nsAutoString sizes;
+  aSourceElement->GetAttr(nsGkAtoms::sizes, sizes);
+  sel->SetSizesFromDescriptor(sizes);
+
+  // If this is the <img> tag, also pull in src as the default source
+  if (!isSourceTag) {
+    MOZ_ASSERT(aSourceElement == this);
+    if (mSrcURI) {
+      sel->SetDefaultSource(mSrcURI, mSrcTriggeringPrincipal);
+    }
+  }
+
+  return sel.forget();
+}
+
+/* static */
+bool HTMLImageElement::SelectSourceForTagWithAttrs(
+    Document* aDocument, bool aIsSourceTag, const nsAString& aSrcAttr,
+    const nsAString& aSrcsetAttr, const nsAString& aSizesAttr,
+    const nsAString& aTypeAttr, const nsAString& aMediaAttr,
+    nsAString& aResult) {
+  MOZ_ASSERT(aIsSourceTag || (aTypeAttr.IsEmpty() && aMediaAttr.IsEmpty()),
+             "Passing type or media attrs makes no sense without aIsSourceTag");
+  MOZ_ASSERT(!aIsSourceTag || aSrcAttr.IsEmpty(),
+             "Passing aSrcAttr makes no sense with aIsSourceTag set");
+
+  if (aSrcsetAttr.IsEmpty()) {
+    if (!aIsSourceTag) {
+      // For an <img> with no srcset, we would always select the src attr.
+      aResult.Assign(aSrcAttr);
+      return true;
+    }
+    // Otherwise, a <source> without srcset is never selected
+    return false;
+  }
+
+  // Would not consider source tags with unsupported media or type
+  if (aIsSourceTag &&
+      ((!aMediaAttr.IsVoid() && !HTMLSourceElement::WouldMatchMediaForDocument(
+                                    aMediaAttr, aDocument)) ||
+       (!aTypeAttr.IsVoid() && !SupportedPictureSourceType(aTypeAttr)))) {
+    return false;
+  }
+
+  // Using srcset or picture <source>, build a responsive selector for this tag.
+  RefPtr<ResponsiveImageSelector> sel = new ResponsiveImageSelector(aDocument);
+
+  sel->SetCandidatesFromSourceSet(aSrcsetAttr);
+  if (!aSizesAttr.IsEmpty()) {
+    sel->SetSizesFromDescriptor(aSizesAttr);
+  }
+  if (!aIsSourceTag) {
+    sel->SetDefaultSource(aSrcAttr);
+  }
+
+  if (sel->GetSelectedImageURLSpec(aResult)) {
+    return true;
+  }
+
+  if (!aIsSourceTag) {
+    // <img> tag with no match would definitively load nothing.
+    aResult.Truncate();
+    return true;
+  }
+
+  // <source> tags with no match would leave source yet-undetermined.
+  return false;
+}
+
+void HTMLImageElement::DestroyContent() {
+  // Clear mPendingImageLoadTask to avoid running LoadSelectedImage() after
+  // getting destroyed.
+  mPendingImageLoadTask = nullptr;
+
+  mResponsiveSelector = nullptr;
+
+  nsImageLoadingContent::Destroy();
+  nsGenericHTMLElement::DestroyContent();
+}
+
+void HTMLImageElement::MediaFeatureValuesChanged() {
+  UpdateSourceSyncAndQueueImageTask(false);
+}
+
+bool HTMLImageElement::ShouldLoadImage() const {
+  return OwnerDoc()->ShouldLoadImages();
+}
+
+void HTMLImageElement::SetLazyLoading() {
+  if (mLazyLoading) {
+    return;
+  }
+
+  // If scripting is disabled don't do lazy load.
+  // https://whatpr.org/html/3752/images.html#updating-the-image-data
+  //
+  // Same for printing.
+  Document* doc = OwnerDoc();
+  if (!doc->IsScriptEnabled() || doc->IsStaticDocument()) {
+    return;
+  }
+
+  doc->EnsureLazyLoadObserver().Observe(*this);
+  mLazyLoading = true;
+  UpdateImageState(true);
+}
+
+void HTMLImageElement::StartLoadingIfNeeded() {
+  if (!LoadingEnabled() || !ShouldLoadImage()) {
+    return;
+  }
+
+  // Use script runner for the case the adopt is from appendChild.
+  // Bug 1076583 - We still behave synchronously in the non-responsive case
+  nsContentUtils::AddScriptRunner(
+      InResponsiveMode()
+          ? NewRunnableMethod<bool>("dom::HTMLImageElement::QueueImageLoadTask",
+                                    this, &HTMLImageElement::QueueImageLoadTask,
+                                    true)
+          : NewRunnableMethod<bool>("dom::HTMLImageElement::MaybeLoadImage",
+                                    this, &HTMLImageElement::MaybeLoadImage,
+                                    true));
+}
+
+void HTMLImageElement::StopLazyLoading(StartLoading aStartLoading) {
+  if (!mLazyLoading) {
+    return;
+  }
+  mLazyLoading = false;
+  Document* doc = OwnerDoc();
+  if (auto* obs = doc->GetLazyLoadObserver()) {
+    obs->Unobserve(*this);
+  }
+
+  if (aStartLoading == StartLoading::Yes) {
+    StartLoadingIfNeeded();
+  }
+}
+
+const StyleLockedDeclarationBlock*
+HTMLImageElement::GetMappedAttributesFromSource() const {
+  if (!IsInPicture() || !mResponsiveSelector) {
+    return nullptr;
+  }
+
+  const auto* source =
+      HTMLSourceElement::FromNodeOrNull(mResponsiveSelector->Content());
+  if (!source) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(IsPreviousSibling(source, this),
+             "Incorrect or out-of-date source");
+  return source->GetAttributesMappedForImage();
+}
+
+void HTMLImageElement::InvalidateAttributeMapping() {
+  if (!IsInPicture()) {
+    return;
+  }
+
+  nsPresContext* presContext = nsContentUtils::GetContextForContent(this);
+  if (!presContext) {
+    return;
+  }
+
+  // Note: Unfortunately, we have to use RESTYLE_SELF, instead of using
+  // RESTYLE_STYLE_ATTRIBUTE or other ways, to avoid re-selector-match because
+  // we are using Gecko_GetExtraContentStyleDeclarations() to retrieve the
+  // extra declaration block from |this|'s width and height attributes, and
+  // other restyle hints seems not enough.
+  // FIXME: We may refine this together with the restyle for presentation
+  // attributes in RestyleManger::AttributeChagned()
+  presContext->RestyleManager()->PostRestyleEvent(
+      this, RestyleHint::RESTYLE_SELF, nsChangeHint(0));
+}
+
+void HTMLImageElement::SetResponsiveSelector(
+    RefPtr<ResponsiveImageSelector>&& aSource) {
+  if (mResponsiveSelector == aSource) {
+    return;
+  }
+
+  mResponsiveSelector = std::move(aSource);
+
+  // Invalidate the style if needed.
+  InvalidateAttributeMapping();
+
+  // Update density.
+  SetDensity(mResponsiveSelector
+                 ? mResponsiveSelector->GetSelectedImageDensity()
+                 : 1.0);
+}
+
+void HTMLImageElement::SetDensity(double aDensity) {
+  if (mCurrentDensity == aDensity) {
+    return;
+  }
+
+  mCurrentDensity = aDensity;
+
+  // Invalidate the reflow.
+  if (nsImageFrame* f = do_QueryFrame(GetPrimaryFrame())) {
+    f->ResponsiveContentDensityChanged();
+  }
+}
+
+void HTMLImageElement::QueueImageLoadTask(bool aAlwaysLoad) {
+  RefPtr<ImageLoadTask> task =
+      new ImageLoadTask(this, aAlwaysLoad, mUseUrgentStartForChannel);
+  // The task checks this to determine if it was the last
+  // queued event, and so earlier tasks are implicitly canceled.
+  mPendingImageLoadTask = task;
+  CycleCollectedJSContext::Get()->DispatchToMicroTask(task.forget());
+}
+
+}  // namespace mozilla::dom