Prevent malformed ICO files from recursively decoding

R=reed@google.com, scroggo@google.com

Author: djsollen@google.com

Review URL: https://codereview.chromium.org/511453002

bug:17265466,17262540
Change-Id: I128b54c74d75b7afca20e47e6650c500278c5adc
(cherry picked from commit 718ef54f748fd12d9b3672e2ff3840370df3df1e)