Fix memory leak in TraceSubscriberStdioImpl.

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 # running overnight and removing outdated bugs/suppressions.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 4895 matching lines @@
    fun:vpx_codec_encode
 }
 {
    bug_115294
    Memcheck:Leak
    fun:_Znw*
    ...
    fun:_ZN17AudioRendererHost14OnCreateStreamEiRK15AudioParameters
 }
 {
-   bug_115411_a
-   Memcheck:Leak
-   fun:_Znw*
-   ...
-   fun:_ZN7content20TraceSubscriberStdioC1ERK8FilePath
-   fun:_ZN48TraceSubscriberStdioTest_CanWriteDataToFile_Test8TestBodyEv
-}
-{
-   bug_115411_b
-   Memcheck:Leak
-   fun:_Znw*
-   ...
-   fun:_ZN7content24TraceSubscriberStdioImpl7OnStartEv
-}
-{
    bug_115419_1
    Memcheck:Uninitialized
    fun:fetch_texel_2d_f_rgba8888
    fun:texture_get_row
    fun:fast_read_rgba_pixels
    fun:read_rgba_pixels
    fun:_swrast_ReadPixels
    fun:_mesa_ReadPixels
    fun:glReadPixels
    fun:_ZN3gpu5gles216GLES2DecoderImpl16HandleReadPixelsEjRKNS0_10ReadPixelsE
@@ skipping 624 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
 }