Valgrind Mac: Suppress an occasional write error.

tools/valgrind/memcheck/suppressions_mac.txt

Index: tools/valgrind/memcheck/suppressions_mac.txt
===================================================================
--- tools/valgrind/memcheck/suppressions_mac.txt	(revision 86248)
+++ tools/valgrind/memcheck/suppressions_mac.txt	(working copy)
@@ -1761,3 +1761,18 @@
    ...
    fun:_ZN6webkit5npapi12_GLOBAL__N_119ReadPlistPluginInfoERK8FilePathP10__CFBundlePNS0_13WebPluginInfoE
 }
+{
+   bug_83566
+   Memcheck:Addr4
+   fun:_ZN7WebCore*V8Entr*Callback11handleEvent*
+   ...
+   fun:_ZN7WebCore16CrossThreadTask3IPN6WebKit31WorkerFileSystemCallbacksBridge*
+   fun:_ZN6WebKit31WorkerFileSystemCallbacksBridge21runTaskOnWorkerThreadEPN7WebCore22ScriptExecutionContextEN3WTF10PassRefPtrIS0_EENS4_10PassOwnPtrINS2_4TaskEEE
+   fun:_ZN7WebCore16CrossThreadTask2IN3WTF10PassRefPtrIN6WebKit31WorkerFileSystemCallbacksBridgeEEES5_NS1_10PassOwnPtrINS_22ScriptExecutionContext4TaskEEES9_E11performTaskEPS7_
+   fun:_ZN7WebCore13WorkerRunLoop4Task11performTaskEPNS_22ScriptExecutionContextE
+   fun:_ZN7WebCore13WorkerRunLoop9runInModeEPNS_13WorkerContextERKNS_13ModePredicateE
+   fun:_ZN7WebCore13WorkerRunLoop3runEPNS_13WorkerContextE
+   fun:_ZN7WebCore12WorkerThread12runEventLoopEv
+   fun:_ZN7WebCore21DedicatedWorkerThread12runEventLoopEv
+   fun:_ZN7WebCore12WorkerThread12workerThreadEv
+}