We need to remove the #ifndef XP_UNIX from browser/base/content/browser.js and browser/base/content/browser-context.inc to enable the Copy Image to Clipboard functionality on Linux/Unix after Bug 21747 is fixed. See the Patch v1.1 attachment on Bug 210043 to see the #ifndef that needs to be removed.
Tweaked the subject. Just for clarification, this is for the enabling the copy image to clipboard frontend on Linux, and not the back-end, which is Bug 21747.
Bug 21747 will fix this.
Fixed by bug 21747.