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

tools/valgrind/memcheck/suppressions_mac.txt

 # There are three kinds of suppressions in this file:
 # 1. Third party stuff we have no control over.
 #
 # 2. Intentional unit test errors, stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing.
 #
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system.
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 2340 matching lines @@
    fun:_ZN27RenderWidgetHostViewMacTest24AddAcceleratedPluginViewEii
    fun:_ZN53RenderWidgetHostViewMacTest_FocusAcceleratedView_Test8TestBodyEv
 }
 {
    bug_112086
    Memcheck:Uninitialized
    fun:x_zone_size
    fun:find_registered_purgeable_zone
    fun:malloc_make_purgeable
 }
+{
+   bug_116526
+   Memcheck:Leak
+   fun:_Znw*
+   ...
+   fun:_ZN4base19SequencedWorkerPoolC*
+   ...
+   fun:_ZN4base46SequencedWorkerPoolTest_DiscardOnShutdown_Test*
+}