Allow the "img.src='';img.src='.." idiom to clear down images immediately.

Source/core/loader/ImageLoader.cpp

Index: Source/core/loader/ImageLoader.cpp
diff --git a/Source/core/loader/ImageLoader.cpp b/Source/core/loader/ImageLoader.cpp
index 3c0d8b679fdac3776145ae9c6e980eae03d51343..147db3536a8078aa7498915b4d61e58b5745402b 100644
--- a/Source/core/loader/ImageLoader.cpp
+++ b/Source/core/loader/ImageLoader.cpp
@@ -353,6 +353,14 @@ void ImageLoader::updateFromElement(UpdateFromElementBehavior updateBehavior)
         doUpdateFromElement(DoNotBypassMainWorldCSP, updateBehavior);
         return;
     }
+    // Allow the idiom "img.src=''; img.src='.." to clear down the image before 
+    // an asynchronous load completes.
+    if (imageSourceURL.isEmpty()) {
+        ImageResource* image = m_image.get();
+        if (image)
+            image->removeClient(this);
+        m_image = nullptr;
+    }
     enqueueImageLoadingMicroTask(updateBehavior);
 }