Ignore the failure of this flaky PDF test.

The Mac 10.6 seems to have a race condition that changes the output.
Disable the test to avoid seeing this failure.

R=edisonn@google.com

Review URL: https://codereview.chromium.org/25887005

git-svn-id: http://skia.googlecode.com/svn/trunk@11593 2bbb7eff-a529-9590-31e7-b0007b416f81

expectations/gm/Test-Mac10.6-MacMini4.1-GeForce320M-x86-Release/expected-results.json

@@ -12295,9 +12295,9 @@
         ]
       ], 
       "bugs": [
-        1578
+        1100
-      ], 
+      ],
-      "reviewed-by-human": false
+      "ignore-failure": true
     }, 
     "tilemode_gradient_pdf-poppler.png": {
       "allowed-digests": [
@@ -12965,4 +12965,4 @@
       "reviewed-by-human": false
     }
   }
-}
+}