cc: Add missing xdisplaycheck data dependency for tests.

cc/cc_tests.gyp

Index: cc/cc_tests.gyp
diff --git a/cc/cc_tests.gyp b/cc/cc_tests.gyp
index 4d29a60996dca6f1dfa5d3020a4446240a2569bb..9daba1137e5e69875a37de677b18c56615cab66f 100644
--- a/cc/cc_tests.gyp
+++ b/cc/cc_tests.gyp
@@ -460,6 +460,15 @@
           'sources': [
             'cc_unittests.isolate',
           ],
+          'conditions': [
+            ['OS=="linux" and use_ozone==0',

[danakj, 2015/03/06 02:30:10]

Can you add a comment for the future, saying what we concluded in this code
review (what GN will have to do, why it is these flags, etc..)?

+              {
+                'dependencies': [
+                  '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
+                ],
+              }
+            ],
+          ],
         },
       ],
     }],