Deleted unused PNG files

In order to remove unused png files inside the chromium source code, I've first wrote a simple python script to narrow my research.

With http://pastebin.com/ZEz4TgzD, I'm doing three things:
- Restricting my search to folders I'm familiar with.
- Listing all strings that end with ".png"
- Grabbing only PNG files that haven't been created in 2014

Then, because I know there might some cases that are not covered, I've looked into *all of them* to make sure they were not used for real anymore.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272080

[François Beaufort, 2014-05-21 13:46:55]

Hello Scott,

Do you mind having a look at this (let's clean) CL?

Thank you,
Francois.

[sky, 2014-05-21 16:09:46]

LGTM

[François Beaufort, 2014-05-21 16:14:10]

The CQ bit was checked by beaufort.francois@gmail.com

[commit-bot: I haz the power, 2014-05-21 19:59:04]

CQ is trying da patch. Follow status at

https://chromium-status.appspot.com/cq/beaufort.francois@gmail.com/296443003/...

[commit-bot: I haz the power, 2014-05-22 03:57:30]

Change committed as 272080