Add compressed/renamed new button style assets from sgabriel.

Simply adds the compressed and renamed asset files for use later.
These will replace the current button style for dialogs, etc.

I renamed the files to *[hover|pressed]_<position>.png for IMAGE_GRID:
https://code.google.com/p/chromium/codesearch#chromium/src/ui/views/painter.h&l=22
I ran build/sanitize-png-files.sh for all files with default level (1).

BUG=155363
TEST=none
R=oshima@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/12383034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@185350 0039d316-1c4b-4281-b951-d872f2087c98