Fix memory leak in SequencedWorkerPool

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 # running overnight and removing outdated bugs/suppressions.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 2340 matching lines @@
    fun:_ZN27RenderWidgetHostViewMacTest24AddAcceleratedPluginViewEii
    fun:_ZN53RenderWidgetHostViewMacTest_FocusAcceleratedView_Test8TestBodyEv
 }
 {
    bug_112086
    Memcheck:Uninitialized
    fun:x_zone_size
    fun:find_registered_purgeable_zone
    fun:malloc_make_purgeable
 }
-{
-   bug_115987_a
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN4base19SequencedWorkerPool5Inner30FinishStartingAdditionalThreadEi
-   fun:_ZN4base19SequencedWorkerPool5Inner*
-}
-{
-   bug_115987_b
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN4base12_GLOBAL__N_123SequencedWorkerPoolTestC2Ev
-   fun:_ZN4base*SequencedWorkerPoolTest_*
-   fun:_ZN4base*SequencedWorkerPoolTest_*
-   fun:_ZN7testing8internal15TestFactoryImplIN4base*SequencedWorkerPoolTest_*
-}
-{
-   bug_115987_c
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN9__gnu_cxx13new_allocatorI10linked_ptrIN4base19SequencedWorkerPool6WorkerEEE8allocateEmPKv
-   fun:_ZNSt12_Vector_baseI10linked_ptrIN4base19SequencedWorkerPool6WorkerEESaIS4_EE11_M_allocateEm
-   fun:_ZNSt6vectorI10linked_ptrIN4base19SequencedWorkerPool6WorkerEESaIS4_EE13_M_insert_auxEN9__gnu_cxx17__normal_iteratorIPS4_S6_EERKS4_
-   fun:_ZNSt6vectorI10linked_ptrIN4base19SequencedWorkerPool6WorkerEESaIS4_EE9push_backERKS4_
-   fun:_ZN4base19SequencedWorkerPool5Inner10ThreadLoopEPNS0_6WorkerE
-   fun:_ZN4base19SequencedWorkerPool6Worker3RunEv
-}