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diff --git a/uriloader/preload/PreloaderBase.h b/uriloader/preload/PreloaderBase.h
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+++ b/uriloader/preload/PreloaderBase.h
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+/* 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/. */
+
+#ifndef PreloaderBase_h__
+#define PreloaderBase_h__
+
+#include "mozilla/Maybe.h"
+#include "mozilla/PreloadHashKey.h"
+#include "mozilla/WeakPtr.h"
+#include "nsCOMPtr.h"
+#include "nsISupports.h"
+#include "nsITimer.h"
+#include "nsIURI.h"
+#include "nsIWeakReferenceUtils.h"
+#include "nsTArray.h"
+
+class nsIChannel;
+class nsINode;
+class nsIRequest;
+class nsIStreamListener;
+
+namespace mozilla {
+
+namespace dom {
+
+class Document;
+
+}  // namespace dom
+
+/**
+ * A half-abstract base class that resource loaders' respective
+ * channel-listening classes should derive from.  Provides a unified API to
+ * register the load or preload in a document scoped service, links <link
+ * rel="preload"> DOM nodes with the load progress and provides API to possibly
+ * consume the data by later, dynamically discovered consumers.
+ *
+ * This class is designed to be used only on the main thread.
+ */
+class PreloaderBase : public SupportsWeakPtr, public nsISupports {
+ public:
+  PreloaderBase() = default;
+
+  // Called by resource loaders to register this preload in the document's
+  // preload service to provide coalescing, and access to the preload when it
+  // should be used for an actual load.
+  void NotifyOpen(const PreloadHashKey& aKey, dom::Document* aDocument,
+                  bool aIsPreload, bool aIsModule = false);
+  void NotifyOpen(const PreloadHashKey& aKey, nsIChannel* aChannel,
+                  dom::Document* aDocument, bool aIsPreload,
+                  bool aIsModule = false);
+
+  // Called when the load is about to be started all over again and thus this
+  // PreloaderBase will be registered again with the same key.  This method
+  // taks care to deregister this preload prior to that.
+  // @param aNewPreloader: If there is a new request and loader created for the
+  // restarted load, we will pass any necessary information into it.
+  void NotifyRestart(dom::Document* aDocument,
+                     PreloaderBase* aNewPreloader = nullptr);
+
+  // Called by the loading object when the channel started to load
+  // (OnStartRequest or equal) and when it finished (OnStopRequest or equal)
+  void NotifyStart(nsIRequest* aRequest);
+  void NotifyStop(nsIRequest* aRequest, nsresult aStatus);
+  // Use this variant only in complement to NotifyOpen without providing a
+  // channel.
+  void NotifyStop(nsresult aStatus);
+
+  // Called by resource loaders or any suitable component to notify the preload
+  // has been used for an actual load.  This is intended to stop any usage
+  // timers.
+  // @param aDropLoadBackground: If `Keep` then the loading channel, if still in
+  // progress, will not be removed the LOAD_BACKGROUND flag, for instance XHR is
+  // the user here.
+  enum class LoadBackground { Keep, Drop };
+  void NotifyUsage(dom::Document* aDocument,
+                   LoadBackground aLoadBackground = LoadBackground::Drop);
+  // Whether this preloader has been used for a regular/actual load or not.
+  bool IsUsed() const { return mIsUsed; }
+
+  // Removes itself from the document's preloads hashtable
+  void RemoveSelf(dom::Document* aDocument);
+
+  // When a loader starting an actual load finds a preload, the data can be
+  // delivered using this method.  It will deliver stream listener notifications
+  // as if it were coming from the resource loading channel.  The |request|
+  // argument will be the channel that loaded/loads the resource.
+  // This method must keep to the nsIChannel.AsyncOpen contract.  A loader is
+  // not obligated to re-implement this method when not necessarily needed.
+  virtual nsresult AsyncConsume(nsIStreamListener* aListener);
+
+  // Accessor to the resource loading channel.
+  nsIChannel* Channel() const { return mChannel; }
+
+  // May change priority of the resource loading channel so that it's treated as
+  // preload when this was initially representing a normal speculative load but
+  // later <link rel="preload"> was found for this resource.
+  virtual void PrioritizeAsPreload() = 0;
+
+  // Helper function to set the LOAD_BACKGROUND flag on channel initiated by
+  // <link rel=preload>.  This MUST be used before the channel is AsyncOpen'ed.
+  static void AddLoadBackgroundFlag(nsIChannel* aChannel);
+
+  // These are linking this preload to <link rel="preload"> DOM nodes.  If we
+  // are already loaded, immediately notify events on the node, otherwise wait
+  // for NotifyStop() call.
+  void AddLinkPreloadNode(nsINode* aNode);
+  void RemoveLinkPreloadNode(nsINode* aNode);
+
+  // A collection of redirects, the main consumer is fetch.
+  class RedirectRecord {
+   public:
+    RedirectRecord(uint32_t aFlags, already_AddRefed<nsIURI> aURI)
+        : mFlags(aFlags), mURI(aURI) {}
+
+    uint32_t Flags() const { return mFlags; }
+    nsCString Spec() const;
+    nsCString Fragment() const;
+
+   private:
+    uint32_t mFlags;
+    nsCOMPtr<nsIURI> mURI;
+  };
+
+  const nsTArray<RedirectRecord>& Redirects() { return mRedirectRecords; }
+
+  void SetForEarlyHints() { mIsEarlyHintsPreload = true; }
+
+ protected:
+  virtual ~PreloaderBase();
+
+  // The loading channel.  This will update when a redirect occurs.
+  nsCOMPtr<nsIChannel> mChannel;
+
+ private:
+  void NotifyNodeEvent(nsINode* aNode);
+  void CancelUsageTimer();
+
+  void ReportUsageTelemetry();
+
+  // A helper class that will update the PreloaderBase.mChannel member when a
+  // redirect happens, so that we can reprioritize or cancel when needed.
+  // Having a separate class instead of implementing this on PreloaderBase
+  // directly is to keep PreloaderBase as simple as possible so that derived
+  // classes don't have to deal with calling super when implementing these
+  // interfaces from some reason as well.
+  class RedirectSink;
+
+  // A timer callback to trigger the unuse warning for this preload
+  class UsageTimer final : public nsITimerCallback, public nsINamed {
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSITIMERCALLBACK
+    NS_DECL_NSINAMED
+
+    UsageTimer(PreloaderBase* aPreload, dom::Document* aDocument);
+
+   private:
+    ~UsageTimer() = default;
+
+    WeakPtr<dom::Document> mDocument;
+    WeakPtr<PreloaderBase> mPreload;
+  };
+
+ private:
+  // Reference to HTMLLinkElement DOM nodes to deliver onload and onerror
+  // notifications to.
+  nsTArray<nsWeakPtr> mNodes;
+
+  // History of redirects.
+  nsTArray<RedirectRecord> mRedirectRecords;
+
+  // Usage timer, emits warning when the preload is not used in time.  Started
+  // in NotifyOpen and stopped in NotifyUsage.
+  nsCOMPtr<nsITimer> mUsageTimer;
+
+  // The key this preload has been registered under.  We want to remember it to
+  // be able to deregister itself from the document's preloads.
+  PreloadHashKey mKey;
+
+  // This overrides the final event we send to DOM nodes to be always 'load'.
+  // Modified in NotifyStart based on LoadInfo data of the loading channel.
+  bool mShouldFireLoadEvent = false;
+
+  // True after call to NotifyUsage.
+  bool mIsUsed = false;
+
+  // True after we have reported the usage telemetry.  Prevent duplicates.
+  bool mUsageTelementryReported = false;
+
+  // True when this is used to Early Hints preload.
+  bool mIsEarlyHintsPreload = false;
+
+  // Emplaced when the data delivery has finished, in NotifyStop, holds the
+  // result of the load.
+  Maybe<nsresult> mOnStopStatus;
+};
+
+}  // namespace mozilla
+
+#endif  // !PreloaderBase_h__