Revert "Add image_diff from the chromium repo."

This reverts commit ac5097e515ce8237ead2c89bc61dc914cb75313b.

Reason for revert:

Breaks compile on the ASan bot (e.g., http://build.chromium.org/p/client.mojo/builders/Mojo%20Linux%20ASan/builds/95/steps/mojob%20build/logs/stdio).

TBR=ojan

Review URL: https://codereview.chromium.org/800773002