--- a/dom/base/nsImageLoadingContent.cpp
+++ b/dom/base/nsImageLoadingContent.cpp
@@ -1367,18 +1367,16 @@ nsImageLoadingContent::PrepareNextReques
 
     mMostRecentRequestChange = now;
   }
 
   // We only want to cancel the existing current request if size is not
   // available. bz says the web depends on this behavior.
   // Otherwise, we get rid of any half-baked request that might be sitting there
   // and make this one current.
-  // TODO: Bug 583491
-  // Investigate/Cleanup NS_ERROR_IMAGE_SRC_CHANGED use in nsImageFrame.cpp
   return HaveSize(mCurrentRequest) ?
            PreparePendingRequest(aImageLoadType) :
            PrepareCurrentRequest(aImageLoadType);
 }
 
 nsresult
 nsImageLoadingContent::SetBlockedRequest(int16_t aContentDecision)
 {

--- a/xpcom/base/ErrorList.py
+++ b/xpcom/base/ErrorList.py
@@ -857,19 +857,16 @@ with modules["URILOADER"]:
     errors["NS_REFRESHURI_HEADER_FOUND"] = SUCCESS(2)
 
 
 
 # =======================================================================
 # 25: NS_ERROR_MODULE_CONTENT
 # =======================================================================
 with modules["CONTENT"]:
-    # Error codes for image loading
-    errors["NS_ERROR_IMAGE_SRC_CHANGED"] = FAILURE(4)
-    errors["NS_ERROR_IMAGE_BLOCKED"] = FAILURE(5)
     # Error codes for content policy blocking
     errors["NS_ERROR_CONTENT_BLOCKED"] = FAILURE(6)
     errors["NS_ERROR_CONTENT_BLOCKED_SHOW_ALT"] = FAILURE(7)
     # Success variations of content policy blocking
     errors["NS_PROPTABLE_PROP_NOT_THERE"] = FAILURE(10)
     # Error code for XBL
     errors["NS_ERROR_XBL_BLOCKED"] = FAILURE(15)
     # Error code for when the content process crashed