Bug 1626517 - Replaced mozilla::Unused with mozilla::Ignore in mozilla::Decoder/mozilla::Encoder calls. r=m_kato

Differential Revision: https://phabricator.services.mozilla.com/D129022

dom/xhr/XMLHttpRequestMainThread.cpp

@@ -530,14 +530,12 @@ nsresult XMLHttpRequestMainThread::AppendToResponseText(
     uint32_t result;
     size_t read;
     size_t written;
-    bool hadErrors;
-    Tie(result, read, written, hadErrors) =
+    Tie(result, read, written, Ignore) =
         mDecoder->DecodeToUTF16(aBuffer, handle.AsSpan().From(len), aLast);
     MOZ_ASSERT(result == kInputEmpty);
     MOZ_ASSERT(read == aBuffer.Length());
     len += written;
     MOZ_ASSERT(len <= destBufferLen.value());
-    Unused << hadErrors;
     handle.Finish(len, false);
   }  // release mutex