Valgrind Mac: Suppress an occasional write error.

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 # running overnight and removing outdated bugs/suppressions.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 1743 matching lines @@
    fun:_ZN3IPC12ChannelProxyC2ERKNS_13ChannelHandleENS_7Channel4ModeEPNS4_8ListenerEPN4base16MessageLoopProxyE
    fun:_ZN3IPC12ChannelProxyC1ERKNS_13ChannelHandleENS_7Channel4ModeEPNS4_8ListenerEPN4base16MessageLoopProxyE
    fun:_ZN36IPCChannelTest_ChannelProxyTest_Test8TestBodyEv
 }
 {
    bug_82682
    Memcheck:Leak
    ...
    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
+}