adjust suppress for uninit error from visitStack

tools/valgrind/memcheck/suppressions.txt

 # There are four kinds of suppressions in this file.
 # 1. third party stuff we have no control over
 #
 # 2. intentional unit test errors, or 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 (but a few aren't yet).
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 6170 matching lines @@
    bug_340752
    Memcheck:Uninitialized
    ...
    fun:_ZN7WebCore17HeapContainsCache*
    fun:_ZN7WebCore11ThreadState19heapPageFromAddressEPh
    fun:_ZN7WebCore11ThreadState19checkAndMarkPointerEPNS_7VisitorEPh
    fun:_ZN7WebCore4Heap19checkAndMarkPointerEPNS_7VisitorEPh
    fun:_ZN7WebCore11ThreadState10visitStackEPNS_7VisitorE
    fun:_ZN7WebCore11ThreadState5traceEPNS_7VisitorE
    fun:_ZN7WebCore11ThreadState10visitRootsEPNS_7VisitorE
-   fun:_ZN7WebCore4Heap14collectGarbageENS_11ThreadState10StackStateENS0_6GCTypeE
+   fun:_ZN7WebCore4Heap14collectGarbageENS_11ThreadState10StackState*
 }
 {
    bug_345432
    Memcheck:Leak
    ...
    fun:_ZN7content14GpuChannelHost7ConnectERKN3IPC13ChannelHandleE
    fun:_ZN7content14GpuChannelHost6CreateEPNS_21GpuChannelHostFactoryERKN3gpu7GPUInfoERKN3IPC13ChannelHandleE
    fun:_ZN7content28BrowserGpuChannelHostFactory21GpuChannelEstablishedEv
    fun:_ZN7content28BrowserGpuChannelHostFactory16EstablishRequest12FinishOnMainEv
    fun:_ZN7content28BrowserGpuChannelHostFactory16EstablishRequest4WaitEv
@@ skipping 66 matching lines @@
    fun:_ZN3gpu12GpuScheduler10PutChangedEv
 }
 {
   bug_361594
   Memcheck:Uninitialized
   ...
   fun:*SkA8_Shader_Blitter*blitH*
   ...
   fun:*content*ScreenshotData*EncodeOnWorker*
 }