Remove suppression for gtk_window_add_accel_group in BrowserWindowGtk::ConnectAccelerators.

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 # running overnight and removing outdated bugs/suppressions.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 758 matching lines @@
 {
    bug_16129b
    Memcheck:Leak
    fun:_Znwj
    fun:_Z11NewCallbackIN11webkit_glue20ImageResourceFetcherERKN6WebKit14WebURLResponseERKSsEPN9Callback2IT0_T1_E4TypeEPT_MSE_FvS9_SA_E
    fun:_ZN11webkit_glue20ImageResourceFetcherC1ERK4GURLP8WebFrameiiP14CallbackRunnerI6Tuple2IPS0_RK8SkBitmapEE
    fun:_ZN11WebViewImpl13DownloadImageEiRK4GURLi
    fun:_ZN10RenderView15OnDownloadImageEiRK4GURLi
 }
 {
-   bug_16153
-   Memcheck:Leak
-   fun:malloc
-   fun:g_malloc
-   ...
-   fun:gtk_window_add_accel_group
-   fun:_ZN16BrowserWindowGtk19ConnectAcceleratorsEv
-   fun:_ZN16BrowserWindowGtkC1EP7Browser
-   fun:_ZN13BrowserWindow19CreateBrowserWindowEP7Browser
-}
-{
    bug_16156
    Memcheck:Leak
    ...
    fun:gtk_im_context_set_cursor_location
    ...
    fun:gtk_widget_size_allocate
 }
 {
    bug_16161
    Memcheck:Leak
@@ skipping 171 matching lines @@
    fun:_ZN7WebCore14ChromiumBridge19clipboardWriteImageEPK15NativeImageSkiaRKNS_4KURLERKNS_6StringE
    fun:_ZN7WebCore10Pasteboard10writeImageEPNS_4NodeERKNS_4KURLERKNS_6StringE
 }
 {
    # Only in test shell
    bug_17188
    Memcheck:Addr4
    fun:_ZN9TestShell10ClosePopupEv
    fun:_ZN12_GLOBAL__N_119MainWindowLostFocusEP10_GtkWidgetP14_GdkEventFocusP9TestShell
 }