angular/angular.js — pull request #9963 by btelles (2014-11-07 21:46:57+00:00)
Title: Why should watchExpression should be idempotent?

This attempts to clarify the rationale. The Previous sentence was a bit ambiguous. If this new explanation does not reflect the intent, please use its active voice (as opposed to passive voice) as a template to clarify the existing sentence.