Remove platform/graphics/Icon.h and all related code.

All of this code (>600 lines) is currently dead, as far as I can tell.
It was used in WebKit, but not in in Chromium port.

The relevant bug for this (http://crbug.com/13225) hasn't been updated (except for label updates) since October 2009, and the last patch set on the next change toward this (https://codereview.chromium.org/174318/show) was uploaded over 3 years ago.

Review URL: https://chromiumcodereview.appspot.com/19594006

git-svn-id: svn://svn.chromium.org/blink/trunk@154737 bbb929c8-8fbe-4397-9dbb-9b2b20218538