Suppress some leaks that seem to be tcmalloc related.

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 # running overnight and removing outdated bugs/suppressions.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 1818 matching lines @@
 {
    bug_30346b
    Memcheck:Addr2
    ...
    fun:_ZSt22__get_temporary_bufferIPN7WebCore11RenderLayerEESt4pairIPT_iEiS5_
    fun:_ZNSt17_Temporary_bufferIPPN7WebCore11RenderLayerES2_EC1ES3_S3_
    fun:_ZN7WebCore11RenderLayer17updateZOrderListsEv
    fun:_ZN7WebCore11RenderLayer24updateLayerListsIfNeededEv
    fun:_ZN7WebCore11RenderLayer38updateCompositingAndLayerListsIfNeededEv
 }
+{
+   http://crbug.com/30436
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_Z10InitModulev
+   fun:pthread_once
+   fun:_ZN15MallocExtension8RegisterEPS_
+   fun:_ZN13TCMallocGuardC1Ev
+}
+{
+   http://crbug.com/30436
+   Memcheck:Param
+   write(buf)
+   obj:/lib/tls/i686/cmov/libc-2.7.so
+   fun:new_do_write
+   fun:_IO_do_write@@GLIBC_2.1
+   fun:_IO_file_overflow@@GLIBC_2.1
+   fun:_IO_switch_to_get_mode
+   fun:_IO_file_seekoff@@GLIBC_2.1
+   fun:_IO_seekoff_unlocked
+   fun:ftell
+   fun:ftell_file_func
+   fun:zipCloseFileInZipRaw
+}
+{
+   http://crbug.com/30436
+   Memcheck:Addr2
+   fun:_ZN8tcmalloc15CentralFreeList14FetchFromSpansEv
+   fun:_ZN8tcmalloc15CentralFreeList18FetchFromSpansSafeEv
+   fun:_ZN8tcmalloc15CentralFreeList11RemoveRangeEPPvS2_i
+   fun:_ZN8tcmalloc11ThreadCache21FetchFromCentralCacheEjj
+   fun:_ZN8tcmalloc11ThreadCache8AllocateEj
+}