3861: Support setting blocks field in review requests the same way as depends_on field is set.

What version are you running?


What's the URL of the page this enhancement relates to, if any?


Describe the enhancement and the motivation for it.

Dependencies between review request are only editable on the blocked review requests' end (depends_on field). Dependencies should be editable from both ends.

What operating system are you using? What browser?

Windows 7 SP1
Firefox 37.0.2

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