Suppress a leak report in mojo's HandleWrapper::Create.

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 # running overnight and removing outdated bugs/suppressions.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 3126 matching lines @@
    ...
    fun:_ZN7content28ShellURLRequestContextGetter20GetURLRequestContextEv
    fun:_ZN7content21ChromeAppCacheService20InitializeOnIOThreadERKN4base8FilePathEPNS_15ResourceContextEPN3net23URLRequestContextGetterE13scoped_refptrIN7storage20SpecialStoragePolicyEE
 }
 {
    bug_587544_b
    Memcheck:Leak
    ...
    fun:_ZN4base4BindIMN7content21ChromeAppCacheServiceEFvRKNS_8FilePathEPNS1_15ResourceContextEPN3net23URLRequestContextGetterE13scoped_refptrIN7storage20SpecialStoragePolicyEEEJPS2_S3_S7_SB_IS9_ESE_EEENS_8CallbackINS_8internal22MakeUnboundRunTypeImplIT_JDpT0_EE4TypeEEESM_DpOSN_
 }
+{
+   bug_600484
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN4mojo3edk2js13HandleWrapper6Create*
+   fun:_ZN3gin9ConverterIN4mojo6Handle*
+   fun:_ZN3gin11ConvertToV8IN4mojo6Handle*
+   fun:_ZN3gin10ToV8TraitsIN4mojo6HandleELb0EE14TryConvertToV8*
+   fun:_ZN3gin14TryConvertToV8IN4mojo6Handle*
+   fun:_ZN3gin10Dictionary3SetIN4mojo6Handle*
+   fun:_ZN4mojo3edk2js12_GLOBAL__N_114CreateDataPipe*
+}