Test extension for extension icon image.

This is essentially part of https://chromiumcodereview.appspot.com/10825012/
Landing it separately so I can run trybots for the mentioned patch.

TEST=none
BUG=none

Review URL: https://chromiumcodereview.appspot.com/10827383

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151919 0039d316-1c4b-4281-b951-d872f2087c98

chrome/test/data/extensions/extension_icon_image/app.json

+{
+  "name": "test",
+  "version": "1",
+  "manifest_version": 2,
+  "icons": { "16": "16.png",
+             "24": "24.png",
+             "48": "48.png" }
+}