Valgrind: Suppress a new variation of a libpng error and widen the mac LoadLibrary suppression.

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 # running overnight and removing outdated bugs/suppressions.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 2747 matching lines @@
 {
    bug_63671
    Memcheck:Param
    write(buf)
    ...
    fun:_ZN9file_util9WriteFileERK8FilePathPKci
    fun:_Z24ConvertWebAppToExtensionRK18WebApplicationInfoRKN4base4TimeE
    fun:_ZN30ExtensionFromWebApp_Basic_Test8TestBodyEv
 }
 {
+   bug_63671_b
+   Memcheck:Param
+   write(buf)
+   ...
+   fun:_ZN9file_util9WriteFileERK8FilePathPKci
+   fun:_ZN12_GLOBAL__N_110SaveBitmapEPSt6vectorIhSaIhEE8FilePathPb
+   fun:_ZN4base8internal15RunnableAdapterIPFvPSt6vectorIhSaIhEE8FilePathPbEE3RunERKS5_RKS6_RKS7_
+}
+{
    bug_64804
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN4base16MessageLoopProxy22currentEv
    ...
    fun:_ZN10URLFetcher4CoreC1EPS_RK4GURLNS_11RequestTypeEPNS_8DelegateE
    fun:_ZN10URLFetcherC*ERK4GURLNS_11RequestTypeEPNS_8DelegateE
 }
 {
    bug_64887_a
@@ skipping 2519 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
 }