Well that seems like some pretty severe backpedaling, since by bringing up past offensive tactics by Google, it was imminently apparent that you were implying this was another example of an offensive tactic.
But regardless of who is good and who is bad (and trust me, I have plenty of bad feelings toward Google myself), this was fundamentally Opera's mistake, not Google's. There is nothing in the ECMAScript standard that says that there is an upper limit on how long a statement can be, and that's the end of the matter.
It is certainly an another example of an anti-competitive tactic and the most probable scenario they achieved it was by ignoring Opera's existence on as many levels of their organization as possible, otherwise it just wouldn't happen -- if you know your "clever trick" doesn't work on one of the browsers, you wouldn't implement the "clever trick" as an universal solution. As such, it's not an accident, it's a consequence of their political decisions (something like "to all our teams: we don't like Opera, do pretend it doesn't exist, do force their users to switch" etc). It's bad enough, no need for more complex "conspiracies."
But regardless of who is good and who is bad (and trust me, I have plenty of bad feelings toward Google myself), this was fundamentally Opera's mistake, not Google's. There is nothing in the ECMAScript standard that says that there is an upper limit on how long a statement can be, and that's the end of the matter.