Fixed memory leaks in download manager unit tests.

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 # running overnight and removing outdated bugs/suppressions.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 4616 matching lines @@
 }
 {
    bug_83626b
    Memcheck:Value4
    fun:_ZNK2v88internal9SparseSet8ContainsEi
    fun:_ZN2v88internal9SparseSet3AddEi
    ...
    fun:_ZN2v88internal20HGlobalValueNumberer41CollectSideEffectsOnPathsToDominatedBlockEPNS0_11HBasicBlockES3_
    fun:_ZN2v88internal20HGlobalValueNumberer12AnalyzeBlockEPNS0_11HBasicBlockEPNS0_9HValueMapE
 }
-{
-   bug_83638
-   Memcheck:Leak
-   fun:_Znw*
-   fun:_ZN43DownloadManagerTest_*_Test8TestBodyEv
-   fun:_ZN7testing8internal38HandleSehExceptionsInMethodIfSupportedINS_4TestEvEET0_PT_MS4_FS3_vEPKc
-   fun:_ZN7testing8internal35HandleExceptionsInMethodIfSupportedINS_4TestEvEET0_PT_MS4_FS3_vEPKc
-
-}
 #-----------------------------------------------------------------------
 # These only occur on our Google workstations
 {
    bug_todo_freeres
    Memcheck:Free
    fun:free
    fun:__libc_freeres
    fun:_vgnU_freeres
    fun:_Exit
    fun:exit
 }
 {
    bug_todo_getdelim
    Memcheck:Leak
    fun:malloc
    fun:getdelim
    ...
    fun:call_init
    fun:_dl_init
 }