Add a suppression for user-after-free in WorkerFileSystemCallbacksBridge::stop.

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 # running overnight and removing outdated bugs/suppressions.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 5820 matching lines @@
    fun:_ZN4aura6client21SetActivationDelegateEPNS_6WindowEPNS0_18ActivationDelegateE
    fun:_ZN24RenderWidgetHostViewAuraC1EP16RenderWidgetHost
    fun:_ZN20RenderWidgetHostView19CreateViewForWidgetEP16RenderWidgetHost
 }
 {
    bug_112803
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN5views45ViewLayerTest_OrphanLayerAfterViewRemove_Test8TestBodyEv
 }
+{
+   bug_112835
+   Memcheck:Unaddressable
+   ...
+   fun:_ZN6WebKit31WorkerFileSystemCallbacksBridge4stopEv
+   fun:_ZN6WebKit31WorkerFileSystemContextObserver10notifyStopEv
+   fun:_ZN7WebCore13WorkerContext21notifyObserversOfStopEv
+   fun:_ZN7WebCore29WorkerThreadShutdownStartTask11performTaskEPNS_22ScriptExecutionContextE
+   fun:_ZN7WebCore13WorkerRunLoop4Task11performTaskERKS0_PNS_22ScriptExecutionContextE
+   fun:_ZN7WebCore13WorkerRunLoop15runCleanupTasksEPNS_13WorkerContextE
+}
 
 #-----------------------------------------------------------------------
 # 4. These only occur on our Google workstations
 
 {
    bug_todo_getdelim
    Memcheck:Leak
    fun:malloc
    fun:getdelim
    ...
    fun:call_init
    fun:_dl_init
 }
 {
    bug_todo_getdelim2
    Memcheck:Leak
    fun:malloc
    fun:getdelim
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
 }
 {
    bug_todo_grep
    Memcheck:Leak
    fun:malloc
    obj:/bin/grep
    obj:/bin/grep
 }