Bug 910533 - Clear invalidation rect only after sync notifying in imgStatusTracker. r=tn a=bajaj

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extra : amend_source : e43b919ff5d86f32a84c6f31ebcde80e18f9e0e4
extra : transplant_source : %EE%F3%81%29%D0%CFnqL%7FQx%84%00N_%9D%25%E88