Fix leak in PrerenderResourceHandlerTest.

tools/heapcheck/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 # running overnight and removing outdated bugs/suppressions.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 1168 matching lines @@
    Heapcheck:Leak
    ...
    fun:IPC::ParamTraits::Read
    fun:IPC::ReadParam
    fun:IPC::MessageWithTuple::Read
    fun:IPC::MessageWithTuple::Dispatch
    fun:ResourceDispatcherHost::OnMessageReceived
    fun:ResourceDispatcherHostTest::MakeTestRequest
 }
 {
-   bug_69414
-   Heapcheck:Leak
-   ...
-   fun:*PrerenderResourceHandlerTest*
-}
-{
    Bug_70062
    Heapcheck:Leak
    fun:PR_NewLock
    fun:InitSessionCacheLocks
    fun:initSessionCacheLocksLazily
    fun:PR_CallOnce
 }