Fix mem leak in sync tests by ensuring that the destruction tasks get to run....

tools/valgrind/memcheck/suppressions.txt

 # There are three 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 # running overnight and removing outdated bugs/suppressions.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 1067 matching lines @@
    fun:_Z10cssyyparsePv
    fun:_ZN7WebCore9CSSParser10parseSheetEPNS_13CSSStyleSheetERKNS_6StringE
 }
 {
    bug_26216
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN9Extension25LoadExtensionActionHelperEPK15DictionaryValuePSs
    fun:_ZN39ExtensionTest_LoadPageActionHelper_Test8TestBodyEv
 }
-{
-   bug_26493
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN12browser_sync6SyncerC1EPN8syncable16DirectoryManagerERKSsPNS_23ServerConnectionManagerEPNS_15ModelSafeWorkerE
-   fun:_ZN12browser_sync12SyncerThread27HandleDirectoryManagerEventERKN8syncable21DirectoryManagerEventE
-   fun:_ZN12SimpleHookupI12EventChannelIN8syncable21DirectoryManagerEventE4Lock8AutoLockES2_N12browser_sync12SyncerThreadEMS7_FvRKS2_EE8CallbackES9_
-   fun:_ZN23EventListenerHookupImplI12EventChannelIN8syncable21DirectoryManagerEventE4Lock8AutoLockES2_12SimpleHookupIS5_S2_N12browser_sync12SyncerThreadEMS8_FvRKS2_EEE11HandleEventESA_
-   fun:_ZN12EventChannelIN8syncable21DirectoryManagerEventE4Lock8AutoLockE15NotifyListenersERKS1_
-   fun:_ZN8syncable16DirectoryManager4OpenERKSs
-   fun:_ZN8sync_api11SyncManager12SyncInternal16SetupForTestModeEPKt
-   fun:_ZN8sync_api11SyncManager16SetupForTestModeEPKt
-   fun:_ZN12browser_sync15SyncBackendHost4Core19DoInitializeForTestEPNS_19BookmarkModelWorkerERKSbIwSt11char_traitsIwESaIwEEPN8sync_api23HttpPostProviderFactoryESC_
-   fun:_Z16DispatchToMethodIN12browser_sync15SyncBackendHost4CoreEMS2_FvPNS0_19BookmarkModelWorkerERKSbIwSt11char_traitsIwESaIwEEPN8sync_api23HttpPostProviderFactoryESD_ES4_S8_SD_SD_EvPT_T0_RK6Tuple4IT1_T2_T3_T4_E
-   fun:_ZN14RunnableMethodIN12browser_sync15SyncBackendHost4CoreEMS2_FvPNS0_19BookmarkModelWorkerERKSbIwSt11char_traitsIwESaIwEEPN8sync_api23HttpPostProviderFactoryESD_E6Tuple4IS4_S8_SD_SD_EE3RunEv
-   fun:_ZN11MessageLoop7RunTaskEP4Task
-   fun:_ZN11MessageLoop21DeferOrRunPendingTaskERKNS_11PendingTaskE
-   fun:_ZN11MessageLoop6DoWorkEv
-   fun:_ZN4base18MessagePumpDefault3RunEPNS_11MessagePump8DelegateE
-   fun:_ZN11MessageLoop11RunInternalEv
-   fun:_ZN11MessageLoop10RunHandlerEv
-}
-{
-   bug_26493
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN9__gnu_cxx13new_allocatorIN21NotificationRegistrar6RecordEE8allocateEjPKv
-   fun:_ZNSt12_Vector_baseIN21NotificationRegistrar6RecordESaIS1_EE11_M_allocateEj
-   fun:_ZNSt6vectorIN21NotificationRegistrar6RecordESaIS1_EE13_M_insert_auxEN9__gnu_cxx17__normal_iteratorIPS1_S3_EERKS1_
-   fun:_ZNSt6vectorIN21NotificationRegistrar6RecordESaIS1_EE9push_backERKS1_
-   fun:_ZN21NotificationRegistrar3AddEP20NotificationObserver16NotificationTypeRK18NotificationSource
-   fun:_ZN12browser_sync139_GLOBAL__N__b_slave_chromium_rel_linux_valgrind_builder_build_src_chrome_browser_sync_util_extensions_activity_monitor.cc_00000000_90D7379F16RegistrationTask3RunEv
-   fun:_ZN11MessageLoop7RunTaskEP4Task
-   fun:_ZN11MessageLoop21DeferOrRunPendingTaskERKNS_11PendingTaskE
-   fun:_ZN11MessageLoop6DoWorkEv
-   fun:_ZN4base18MessagePumpDefault3RunEPNS_11MessagePump8DelegateE
-   fun:_ZN11MessageLoop11RunInternalEv
-   fun:_ZN11MessageLoop10RunHandlerEv
-}