Fix a leak that only happens in layout test mode.

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 # running overnight and removing outdated bugs/suppressions.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 893 matching lines @@
    fun:_ZN7WebCore5Frame4initEv
 }
 {
    # Anonymous namespaces requires wildcard to match on both mac and linux
    bug_17129
    Memcheck:Leak
    fun:_Znw*
    fun:*UtilityProcessHostTest_ExtensionUnpacker_Test8TestBodyEv
 }
 {
-   bug_17184
-   Memcheck:Leak
-   fun:malloc
-   fun:_ZN3WTF10fastMallocEj
-   fun:_ZN7WebCore10StringImplnwEj
-   fun:_ZN7WebCore10StringImpl5adoptERN3WTF6VectorItLj0EEE
-   fun:_ZN7WebCore12createMarkupEPKNS_5RangeEPN3WTF6VectorIPNS_4NodeELj0EEENS_23EAnnotateForInterchangeEb
-   fun:_ZN7WebCore10Pasteboard14writeSelectionEPNS_5RangeEbPNS_5FrameE
-}
-{
    bug_17185
    Memcheck:Leak
    fun:malloc
    fun:_ZN3WTF10fastMallocEj
    fun:_ZN7WebCore10StringImpl19createUninitializedEjRPt
    ...
    fun:_ZN7WebCore10Pasteboard14writeSelectionEPNS_5RangeEbPNS_5FrameE
 }
 {
    bug_17187
@@ skipping 23 matching lines @@
    fun:_ZN3IPC7Channel11ChannelImplC1ERKSsNS0_4ModeEPNS0_8ListenerE
    fun:_ZN3IPC7ChannelC2ERKSsNS0_4ModeEPNS0_8ListenerE
    fun:_ZN3IPC7ChannelC1ERKSsNS0_4ModeEPNS0_8ListenerE
    fun:_ZN3IPC12ChannelProxy7Context13CreateChannelERKSsRKNS_7Channel4ModeE
    fun:_ZN3IPC12ChannelProxy4InitERKSsNS_7Channel4ModeEP11MessageLoopb
    fun:_ZN3IPC12ChannelProxyC2ERKSsNS_7Channel4ModeEP11MessageLoopPNS0_7ContextEb
    fun:_ZN3IPC11SyncChannelC2ERKSsNS_7Channel4ModeEPNS3_8ListenerEPNS_12ChannelProxy13MessageFilterEP11MessageLoopbPN4base13WaitableEventE
    fun:_ZN3IPC11SyncChannelC1ERKSsNS_7Channel4ModeEPNS3_8ListenerEPNS_12ChannelProxy13MessageFilterEP11MessageLoopbPN4base13WaitableEventE
    fun:_ZN11ChildThread4InitEv
 }