clang/win: Try to fix 64-bit build after https://codereview.chromium.org/1261953003.
clang/win: Try to fix 64-bit build after https://codereview.chromium.org/1261953003.

BUG=505316
TBR=cevans

Review URL: https://codereview.chromium.org/1273693004.

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@200223 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk