Add a yet another suppression rule for Bug 16089.

This change adds a yet another suppression rule for the leak in PosixDynamicThreadPool::AddTask(). (As written in Bug 16089, PlatformThread::CreateNonJoinable() does not delete WorkerThread objects created by PosixDynamicThreadPool::AddTask().)

TBR=dhollowa
BUG=16089
TEST=make the "Linux Tests (valgrind)(4)" bot and the "Chromium OS Tests (valgrind)(5)" bot green.
Review URL: https://chromiumcodereview.appspot.com/10700181

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@146288 0039d316-1c4b-4281-b951-d872f2087c98

tools/valgrind/memcheck/suppressions.txt

@@ -1147,6 +1147,15 @@
    ...
    fun:_ZN7fileapi18FileWriterDelegate5WriteEv
 }
+{
+   # ditto, but for unit tests.
+   bug_16089h
+   Memcheck:Leak
+   ...
+   fun:_ZN4base22PosixDynamicThreadPool8PostTask*
+   ...
+   fun:_ZN3net17URLRequestFileJob5StartEv
+}
 {
    # very common in ui tests
    bug_16091