Change log:
https://github.com/google/closure-compiler/compare/a13d0ba6d2b02b2188137b36cb699415bd8784c5...71ab0eecc33e2d8db1ce9ee251cbf174bddc493b
chrome_extensions.js: 927e44d6e32d7b2f50ddb2b20f6515b79a0914b3 -> 3444857184440010d5703dfaf6617eca79b2dab4
polymer-1.0.js: cc53ce238def6597f71ddd75e961011edb18e6a3 -> 55e962227e676cd30f81439573771326933aae54

Latest version includes a fix for using let/const with ChromePass, at
https://github.com/google/closure-compiler/commit/38f6437482b6d660371342469e9bd062613b25d4.

TBR=dbeam@chromium.org

BUG: 671426
Change-Id: Icf80fa1dd526e3cb87cc528d84a0a9540bf85e97
Reviewed-on: https://chromium-review.googlesource.com/567678
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Dan Beam (no longer on Chrome) <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486279}