Bug 1020743: Fix bug in which we don't keep track of which clipboard we cached, general or find, which resulted in pasting from the wrong clipboard on OS X. r=bz, a=sylvestre

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extra : transplant_source : W%7C%1D%D3%FC%02H%83%FA%FE%3E%80%EAZO%8B%F7%EF%84%7E