Make WeakPtr thread-safe, i.e. allow cross-thread copying of WeakPtr

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 # running overnight and removing outdated bugs/suppressions.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 5346 matching lines @@
    fun:_ZN3IPC11SyncChannelC1ERKNS_13ChannelHandleENS_7Channel4ModeEPNS4_8ListenerEPN4base16MessageLoopProxyEbPNS8_13WaitableEventE
    fun:_ZN16ServiceIPCServer13CreateChannelEv
    fun:_ZN16ServiceIPCServer4InitEv
    fun:_ZN14ServiceProcess10InitializeEP16MessageLoopForUIRK11CommandLineP19ServiceProcessState
    fun:_Z18ServiceProcessMainRK18MainFunctionParams
    fun:_ZN12_GLOBAL__N_123RunNamedProcessTypeMainERKSsRK18MainFunctionParams
    fun:ChromeMain
    fun:main
 }
 
+{
+   bug_94345
+   Memcheck:Leak
+   fun:_Znw*
+   fun:_ZNK4base8internal18WeakReferenceOwner6GetRefEv
+   fun:_ZN4base15SupportsWeakPtrI16ObserverListBaseIN11MessageLoop12TaskObserverEEE9AsWeakPtrEv
+   fun:_ZN16ObserverListBaseIN11MessageLoop12TaskObserverEE8IteratorC1ERS2_
+   fun:_ZN11MessageLoop7RunTaskERKNS_11PendingTaskE
+}
+
 #-----------------------------------------------------------------------
 # 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
 }
 {
    bug_todo_getdelim2
    Memcheck:Leak
    fun:malloc
    fun:getdelim
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
    obj:/lib/libselinux.so.1
 }