Our designers generated assets that do not use sRGB color profile
and this makes libpng unhappy. According to jreck@ Android does not use
these profiles. This CL removes all these color profiles using this command:
find . -type f -name "*.png" -exec convert {} -strip {} \;

BUG=394138
R=dtrainor@chromium.org, newt@chromium.org
TBR=tedchoc@chromium.org

Review URL: https://codereview.chromium.org/510423002

Cr-Commit-Position: refs/heads/master@{#292446}