Bug 1067541. Image preloads should not keep going once the actual image has started and gotten canceled. r=peterv

dom/base/nsDocument.cpp

@@ -9593,7 +9593,22 @@ nsDocument::MaybePreLoadImage(nsIURI* uri, const nsAString &aCrossOriginAttr,
   // the "real" load occurs. Unpinned in DispatchContentLoadedEvents and
   // unlink
   if (NS_SUCCEEDED(rv)) {
-    mPreloadingImages.AppendObject(request);
+    mPreloadingImages.Put(uri, request.forget());
+  }
+}
+
+void
+nsDocument::ForgetImagePreload(nsIURI* aURI)
+{
+  // Checking count is faster than hashing the URI in the common
+  // case of empty table.
+  if (mPreloadingImages.Count() != 0) {
+    nsCOMPtr<imgIRequest> req;
+    mPreloadingImages.Remove(aURI, getter_AddRefs(req));
+    if (req) {
+      // Make sure to cancel the request so imagelib knows it's gone.
+      req->CancelAndForgetObserver(NS_BINDING_ABORTED);
+    }
   }
 }
 

dom/base/nsDocument.h

@@ -1094,6 +1094,7 @@ public:
   virtual void MaybePreLoadImage(nsIURI* uri,
                                  const nsAString &aCrossOriginAttr,
                                  ReferrerPolicy aReferrerPolicy) MOZ_OVERRIDE;
+  virtual void ForgetImagePreload(nsIURI* aURI) MOZ_OVERRIDE;
 
   virtual void PreloadStyle(nsIURI* uri, const nsAString& charset,
                             const nsAString& aCrossOriginAttr,
@@ -1742,8 +1743,11 @@ private:
 
   nsExternalResourceMap mExternalResourceMap;
 
-  // All images in process of being preloaded
-  nsCOMArray<imgIRequest> mPreloadingImages;
+  // All images in process of being preloaded.  This is a hashtable so
+  // we can remove them as the real image loads start; that way we
+  // make sure to not keep the image load going when no one cares
+  // about it anymore.
+  nsRefPtrHashtable<nsURIHashKey, imgIRequest> mPreloadingImages;
 
   nsRefPtr<mozilla::dom::DOMImplementation> mDOMImplementation;
 

dom/base/nsIDocument.h

@@ -146,8 +146,8 @@ struct FullScreenOptions {
 } // namespace mozilla
 
 #define NS_IDOCUMENT_IID \
-{ 0x1f343423, 0x957c, 0x4da3, \
-  { 0xaa, 0xa3, 0x07, 0x37, 0x54, 0x3e, 0x79, 0x2a } }
+{ 0xf63d2f6e, 0xd1c1, 0x49b9, \
+ { 0x88, 0x26, 0xd5, 0x9e, 0x5d, 0x72, 0x2a, 0x42 } }
 
 // Enum for requesting a particular type of document when creating a doc
 enum DocumentFlavor {
@@ -1922,6 +1922,12 @@ public:
                                  const nsAString& aCrossOriginAttr,
                                  ReferrerPolicy aReferrerPolicy) = 0;
 
+  /**
+   * Called by images to forget an image preload when they start doing
+   * the real load.
+   */
+  virtual void ForgetImagePreload(nsIURI* aURI) = 0;
+
   /**
    * Called by nsParser to preload style sheets.  Can also be merged into the
    * parser if and when the parser is merged with libgklayout.  aCrossOriginAttr

dom/base/nsImageLoadingContent.cpp

@@ -893,6 +893,11 @@ nsImageLoadingContent::LoadImage(nsIURI* aNewURI,
                                  getter_AddRefs(req),
                                  policyType);
 
+  // Tell the document to forget about the image preload, if any, for
+  // this URI, now that we might have another imgRequestProxy for it.
+  // That way if we get canceled later the image load won't continue.
+  aDocument->ForgetImagePreload(aNewURI);
+
   if (NS_SUCCEEDED(rv)) {
     TrackImage(req);
     ResetAnimationIfNeeded();