Bug 444931. prevent network load of an img with the same URL as the HTML document that included it in order to prevent aborting the HTTP load early and losing the persistent connection. r+sr=bzbarsky

content/base/src/nsImageLoadingContent.cpp

@@ -486,6 +486,22 @@ nsImageLoadingContent::LoadImage(const nsAString& aNewURI,
   NS_ENSURE_SUCCESS(rv, rv);
   // XXXbiesi fire onerror if that failed?
 
+  PRBool equal;
+
+  if (aNewURI.IsEmpty() &&
+      doc->GetDocumentURI() &&
+      NS_SUCCEEDED(doc->GetDocumentURI()->Equals(imageURI,&equal)) && 
+      equal)  {
+
+    // Loading an embedded img from the same URI as the document URI will not work
+    // as a resource cannot recursively embed itself. Attempting to do so generally
+    // results in having to pre-emptively close down an in-flight HTTP transaction 
+    // and then incurring the significant cost of establishing a new TCP channel.
+    // This is generally triggered from <img src=""> 
+    // In light of that, just skip loading it..
+    return NS_OK;
+  }
+
   NS_TryToSetImmutable(imageURI);
 
   return LoadImage(imageURI, aForce, aNotify, doc);