Provide a custom icon for the Chrome Apps folder on Mac.

The folder Chrome apps are installed to currently looks like a boring,
regular folder. It should be cooler.

This adds a folder icon overlay to brand the system-provided
NSImageNameFolder with a logo representing Chrome Apps. When creating
the Chrome Apps folder, the folder icon is composited at runtime and
saved on the folder using NSWorkspace routines.

The png overlay icon assets are crushed, and sum to 34kB in size. See
http://crbug.com/305373#c14 for a screengrab of the appearance in
Finder.

BUG=305373
TEST=On Mac, Install a new packaged app (e.g. Keep). After this, the
Chrome [Canary] Apps folder in /Users/login/Applications should have a
custom icon.

Review URL: https://codereview.chromium.org/149393003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249494 0039d316-1c4b-4281-b951-d872f2087c98
Blink roll 166610:166619

http://build.chromium.org/f/chromium/perf/dashboard/ui/changelog_blink.html?url=/trunk&range=166611:166619&mode=html
TBR=
BUG=

Review URL: https://codereview.chromium.org/152513011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249495 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249496 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249496