Add a suppression for DispatchEvent leak while I look into it.

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 # running overnight and removing outdated bugs/suppressions.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 4639 matching lines @@
    ...
    fun:_ZN14TestingProfile16GetWebKitContextEv
 }
 {
    bug_85151_b
    Memcheck:Leak
    fun:_Znw*
    ...
    fun:_ZN28WebKitContextTest_Basic_Test8TestBodyEv
 }
+{
+   bug_85641
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZN20ExtensionEventRouter13DispatchEventEPN3IPC7Message6SenderERKSsS5_S5_RK4GURL
+   fun:_ZN30ExtensionWebRequestEventRouter13DispatchEventEiPN3net10URLRequestERKSt6vectorIPKNS_13EventListenerESaIS6_EERK9ListValue
+}
 
 #-----------------------------------------------------------------------
 # These only occur on our Google workstations
 {
    bug_todo_freeres
    Memcheck:Free
    fun:free
    fun:__libc_freeres
    fun:_vgnU_freeres
    fun:_Exit
@@ skipping 10 matching lines @@
 }
 {
    bug_todo_getdelim2
    Memcheck:Leak
    fun:malloc
    fun:getdelim
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
 }