Latest compiler version does not include Chrome's externs by default. They
need to be explicitly included.

Change log:
https://github.com/google/closure-compiler/compare/8fc82299c45b0a33f19834222acda4850fd77bc0...5cae9b78a16a2655627733b66d1c686d5f547925
chrome.js: 7ef3422e1e87480d560247d75fee181b4cac24d9
chrome_extensions.js: 3a0b0052782af3f0bd3a5fe10bb568cdd769db4e -> 03c824e85e7b77bde4e7449ed3727608b05b2acc
polymer-1.0.js: 55e962227e676cd30f81439573771326933aae54 -> 8f3b8c9354813ae0e2f186bf2f504cf3f3182a66

BUG=831004

Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I0db559ee9a198dadd3b23e57b835cc6b985540a9
Reviewed-on: https://chromium-review.googlesource.com/1006182Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551058}