[Sync] Consolidate DataTypeController methods that post on the backend thread

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 # running overnight and removing outdated bugs/suppressions.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 4894 matching lines @@
    fun:_ZN21RenderViewHostManager14InitRenderViewEP14RenderViewHostRKN7content19NavigationEntryImplE
    fun:_ZN21RenderViewHostManager8NavigateERKN7content19NavigationEntryImplE
    fun:_ZN11TabContents15NavigateToEntryERKN7content19NavigationEntryImplENS0_20NavigationController10ReloadTypeE
    fun:_ZN11TabContents22NavigateToPendingEntryEN7content20NavigationController10ReloadTypeE
    fun:_ZN24NavigationControllerImpl22NavigateToPendingEntryEN7content20NavigationController10ReloadTypeE
    fun:_ZN24NavigationControllerImpl9LoadEntryEPN7content19NavigationEntryImplE
    fun:_ZN24NavigationControllerImpl7LoadURLERK4GURLRKN7content8ReferrerENS3_14PageTransitionERKSs
    fun:_ZN11BalloonHost4InitEv
 }
 {
-   bug_105667_a
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN12browser_sync26TypedUrlDataTypeController21StartAssociationAsync*
-   fun:_ZN12browser_sync29NonFrontendDataTypeController5Start*
-   fun:_ZN12browser_sync19DataTypeManagerImpl13StartNextTypeEv
-   fun:_ZN12browser_sync19DataTypeManagerImpl13DownloadReady*
-}
-{
-   bug_105667_b
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN12browser_sync26TypedUrlDataTypeController20StopAssociationAsyncEv
-   fun:_ZN12browser_sync29NonFrontendDataTypeController4StopEv
-   fun:_ZN12browser_sync19DataTypeManagerImpl10FinishStopEv
-   fun:_ZN12browser_sync19DataTypeManagerImpl4StopEv
-   ...
-   fun:_ZN18ProfileSyncService8Shutdown*
-   fun:_ZN18ProfileSyncServiceD2Ev
-   ...
-   fun:_ZN22TestProfileSyncServiceD0Ev
-   ...
-   fun:_ZN10scoped_ptrI22TestProfileSyncServiceE5resetEPS0_
-   fun:_ZN30ProfileSyncServiceTypedUrlTest8TearDownEv
-}
-{
    bug_105715
    Memcheck:Uninitialized
    ...
    fun:vfprintf
    fun:__vsnprintf_chk
    fun:_ZN4base9vsnprintfEPcjPKcS0_
    fun:_ZN4base12_GLOBAL__N_110vsnprintfTEPcjPKcS1_
    fun:_ZN4base12_GLOBAL__N_1L14StringAppendVTISsEEvPT_PKNS2_10value_typeEPc
    fun:_ZN4base13StringAppendVEPSsPKcPc
    fun:_ZN4base13StringAppendFEPSsPKcz
@@ skipping 767 matching lines @@
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
 }
 {
    bug_todo_grep
    Memcheck:Leak
    fun:malloc
    obj:/bin/grep
    obj:/bin/grep
 }