Reproducible on: Nightly 39.0a1 (2015-03-18) Affected platforms: Ubuntu 14.04 (x64), Windows 7 (x64), Mac OS X 10.9.5. Preconditions: * browser.readinglist.enabled = true * user is having a high-contrast theme set or the Developer Edition theme Steps to reproduce: 1. Launch Firefox. 2. Access a web page, (e.g.) https://www.mozilla.org/en-US/mission/. 3. Check the "Add page to Reading List" button from the Location Bar. Expected result: The "Add page to Reading List" button icon is adapting properly to high-contrast themes or Firefox Developer Edition's theme. Actual result: The "Add page to Reading List" button icon does not change in any way to ensure its compatibility with high-contrast or developer edition themes. Note: * Although the "Add page to Reading List" button has not yet landed on m-a, I'm pretty sure it's the same case as with the Reader View's "Enter Reader View" button, where we have the same issue.