gcdPrivate API: Update to new API spec for confirmCode to add code param.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=75242002
Refactor to simplify transpilation of destructuring patterns in param lists.

Now we just convert them to var statements in the function body, then they'll get transpiled to valid ES3 by visitObjectPattern or visitArrayPattern.

This CL also fixes a couple small issues with computed properties.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=75243091