Valgrind Mac: Update a suppression for a leak.

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 # running overnight and removing outdated bugs/suppressions.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 1510 matching lines @@
    fun:_Z16CMMProcessBitmapP15CMMBitmapParams
    fun:DoMatchBitmap
    fun:CWMatchBitmap
    fun:ConvertImageGeneric
    fun:CMSColorWorldConvertData
    fun:CMSTransformConvertData
    fun:CGCMSInterfaceTransformConvertData
    fun:CGColorTransformConvertData
 }
 {
-   bug_52681
+   bug_52681_a
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN16ChildProcessHost13CreateChannelEv
    fun:_ZN18UtilityProcessHost12StartProcessERK8FilePath
    fun:_ZN18UtilityProcessHost22StartExtensionUnpackerERK8FilePath
    fun:_ZN14RunnableMethodI26SandboxedExtensionUnpackerMS0_FvRK8FilePathE6Tuple1IS1_EE3RunEv
    fun:_ZN11MessageLoop7RunTaskEP4Task
-   fun:_ZN11MessageLoop21DeferOrRunPendingTaskERKNS_11PendingTaskE
-   fun:_ZN11MessageLoop6DoWorkEv
-   fun:_ZN4base19MessagePumpLibevent3RunEPNS_11MessagePump8DelegateE
-   fun:_ZN11MessageLoop11RunInternalEv
 }
+{
+   bug_52681_b
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN16ChildProcessHost13CreateChannelEv
+   fun:_ZN18UtilityProcessHost12StartProcessERK8FilePath
+   fun:_ZN18UtilityProcessHost22StartExtensionUnpackerERK8FilePath
+   fun:_ZN26SandboxedExtensionUnpacker22StartProcessOnIOThreadERK8FilePath
+   fun:_Z16DispatchToMethodI26SandboxedExtensionUnpackerMS0_FvRK8FilePathES1_EvPT_T0_RK6Tuple1IT1_E
+   fun:_ZN14RunnableMethodI26SandboxedExtensionUnpackerMS0_FvRK8FilePathE6Tuple1IS1_EE3RunEv
+   fun:_ZN11MessageLoop7RunTaskEP4Task
+}