Fix incorrect comment about XMLHttpRequest::handleDidCancel()

Source/core/xml/XMLHttpRequest.h

Index: Source/core/xml/XMLHttpRequest.h
diff --git a/Source/core/xml/XMLHttpRequest.h b/Source/core/xml/XMLHttpRequest.h
index 5b6abc437918101b27e896c7360ac00c805ce47c..f15701f1db7a3412c571f67f3f715be8f794e935 100644
--- a/Source/core/xml/XMLHttpRequest.h
+++ b/Source/core/xml/XMLHttpRequest.h
@@ -211,7 +211,9 @@ private:
     void handleDidFailGeneric();
     // Handles didFail() call not caused by cancellation or timeout.
     void handleNetworkError();
-    // Handles didFail() call triggered by m_loader->cancel().
+    // Handles didFail() call for cancellations. For example, the
+    // ResourceLoader handling the load notifies m_loader of an error
+    // cancellation when the frame containing the XHR navigates away.
     void handleDidCancel();
     // Handles didFail() call for timeout.
     void handleDidTimeout();