Suppress leak of ProcessSingleton::LinuxWatcher on shutdown.

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 # running overnight and removing outdated bugs/suppressions.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 5195 matching lines @@
    fun:HB_ShapeItem
    fun:_ZN7WebCore21ComplexTextController11shapeGlyphsEv
    fun:_ZN7WebCore21ComplexTextController13nextScriptRunEv
    fun:_ZN7WebCore21ComplexTextController14widthOfFullRunEv
    fun:_ZNK7WebCore4Font24floatWidthForComplexTextERKNS_7TextRunEPN3WTF7HashSetIPKNS_14SimpleFontDataENS4_7PtrHashIS8_EENS4_10HashTraitsIS8_EEEEPNS_13GlyphOverflowE
    fun:_ZNK7WebCore4Font5widthERKNS_7TextRunERiRN3WTF6StringE
    fun:_ZN7WebCore14SVGTextMetricsC1EPNS_19RenderSVGInlineTextERKNS_7TextRunE
    fun:_ZN7WebCore14SVGTextMetrics21measureCharacterRangeEPNS_19RenderSVGInlineTextEjj
    fun:_ZNK7WebCore30SVGTextLayoutAttributesBuilder25propagateLayoutAttributesEPNS_12RenderObjectERN3WTF6VectorINS_23SVGTextLayoutAttributesELm0EEERjRt
 }
+{
+   # ProcessSingleton::LinuxWatcher is marked DeleteOnIOThread.  Sometimes it
+   # leaks on shutdown instead of getting deleted.  The destructor doesn't do
+   # anything important, so this shouldn't be a big deal.
+   bug_104578
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN16ProcessSingletonC1ERK8FilePath
+   fun:_ZN22ChromeBrowserMainParts25PreMainMessageLoopRunImplEv
+}
 
 #-----------------------------------------------------------------------
 # 4. These only occur on our Google workstations
 {
    bug_todo_freeres
    Memcheck:Free
    fun:free
    fun:__libc_freeres
    fun:_vgnU_freeres
    fun:_Exit
@@ skipping 17 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
 }