Revert "Add image_diff from the chromium repo."

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

Committed: https://chromium.googlesource.com/external/mojo/+/79d76b3da8f72ca3affaaaf2821b1d0bb212f522

[blundell, 2014-12-12 07:07:56]

Committed patchset #1 (id:1) manually as
79d76b3da8f72ca3affaaaf2821b1d0bb212f522 (presubmit successful).