back out CLs 21367, 21366 - no idea why these keep breaking

chrome/chrome.gyp

Index: chrome/chrome.gyp
===================================================================
--- chrome/chrome.gyp	(revision 21369)
+++ chrome/chrome.gyp	(working copy)
@@ -3290,6 +3290,18 @@
       ],
     },
     {
+      'target_name': 'image_diff',
+      'type': 'executable',
+      'msvs_guid': '50B079C7-CD01-42D3-B8C4-9F8D9322E822',
+      'dependencies': [
+        '../base/base.gyp:base',
+        '../base/base.gyp:base_gfx',
+      ],
+      'sources': [
+        'tools/test/image_diff/image_diff.cc',
+      ],
+    },
+    {
       # This target contains mocks and test utilities that don't belong in
       # production libraries but are used by more than one test executable.
       'target_name': 'test_support_common',