I see four copies of this URI in memory at startup, plus another copy in some giant JSON as the data for a key of _dataURL.

Which is 42kb just for the Yahoo icon.

For context, we support installing arbitrary search engines, and their icons are specified in the OpenSearch description file (XML) as base64 encoded data: URIs generally. This includes our built-in engines. We could probably change the built-in engines to refer to chrome:// URIs instead, but it would complicate things a bit (requiring some search service tweaks, makes the search engine definitions not self-contained and so harder to maintain, etc.), so I'd want to avoid that unless it's a significant win.

Here's an example of the search engine icon: http://mxr.mozilla.org/mozilla-central/source/browser/locales/en-US/searchplugins/yahoo.xml All of them are defined on a single line, so they shouldn't hit the problem that the Google icon had.

They're also in XML files, and so not parsed by the JS engine :)