Remove text and private chunks from png images

Remove text and private chunks from png images

Removing tEXt, iTXt, tIME, mk*, prVW, and vpAg chunks saves over 2 MB. The biggest savings is from iTXt chunks containing XML, seemingly left by Adobe ImageReady, which totaled 1.6 MB in 1600 files.

Also update chrome/app/theme/README with extra pngcrush flags to drop the worst offenders.

Chunks I left in place but that we may not need: cHRM, gAMA, iCCP, pHYs, sBIT.


TBR=ben@chromium.org
BUG=146632
TEST=pngtopnm|md5sum unchanged for all affected images

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=157065

[benrg, 2012-09-15 01:48:52]

Oshima, PTAL. The upload failed part way through (after nearly an hour), but I
think everything was uploaded except some of the before and after PNGs, which
are useless anyway.

[oshima, 2012-09-15 02:09:23]

LGTM

We also need some announcement and talk to UX team about this, but we can do
that next week. Thank you for finding & fixing this.

[benrg, 2012-09-17 02:28:39]

Ben, owner permission (2124 PNGs and one README).

[Ben Goodger (Google), 2012-09-17 16:08:55]

On 2012/09/17 02:28:39, benrg wrote:
> Ben, owner permission (2124 PNGs and one README).

lgtm