Suppress a leak in base::SequencedWorkerPool (issue 116526)

TBR=dhollowa
BUG=116526,79878
Review URL: https://chromiumcodereview.appspot.com/9585013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@124634 0039d316-1c4b-4281-b951-d872f2087c98

tools/valgrind/memcheck/suppressions_mac.txt

@@ -2358,3 +2358,12 @@
    fun:find_registered_purgeable_zone
    fun:malloc_make_purgeable
 }
+{
+   bug_116526
+   Memcheck:Leak
+   fun:_Znw*
+   ...
+   fun:_ZN4base19SequencedWorkerPoolC*
+   ...
+   fun:_ZN4base46SequencedWorkerPoolTest_DiscardOnShutdown_Test*
+}