Auto merge of #12921 - paulrouget:imgOnError, r=nox

Trigger image.onerror

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #12885 (github issue number if applicable).

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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1 files changed, 9 insertions, 4 deletions

diff --git a/components/script/dom/htmlimageelement.rs b/components/script/dom/htmlimageelement.rs
index cb0f65d0b2b..f03e43d9f2e 100644
--- a/components/script/dom/htmlimageelement.rs
+++ b/components/script/dom/htmlimageelement.rs
@@ -86,14 +86,14 @@ impl Runnable for ImageResponseHandlerRunnable {
         // Update the image field
         let element = self.element.root();
         let element_ref = element.r();
-        let (image, metadata, trigger_image_load) = match self.image {
+        let (image, metadata, trigger_image_load, trigger_image_error) = match self.image {
             ImageResponse::Loaded(image) | ImageResponse::PlaceholderLoaded(image) => {
-                (Some(image.clone()), Some(ImageMetadata { height: image.height, width: image.width } ), true)
+                (Some(image.clone()), Some(ImageMetadata { height: image.height, width: image.width } ), true, false)
             }
             ImageResponse::MetadataLoaded(meta) => {
-                (None, Some(meta), false)
+                (None, Some(meta), false, false)
             }
-            ImageResponse::None => (None, None, true)
+            ImageResponse::None => (None, None, false, true)
         };
         element_ref.current_request.borrow_mut().image = image;
         element_ref.current_request.borrow_mut().metadata = metadata;
@@ -107,6 +107,11 @@ impl Runnable for ImageResponseHandlerRunnable {
             element.upcast::<EventTarget>().fire_simple_event("load");
         }
 
+        // Fire image.onerror
+        if trigger_image_error {
+            element.upcast::<EventTarget>().fire_simple_event("error");
+        }
+
         // Trigger reflow
         let window = window_from_node(document.r());
         window.add_pending_reflow();