Fix data race in IPC::ChannelProxy

Fixes a missing lock acquisition from the listener thread when
accessing |channel_|.

Also removes the TSAN suppression for this bug.

BUG=628481
TBR=glider@chromium.org for suppression removal

Review-Url: https://codereview.chromium.org/2158893002
Cr-Commit-Position: refs/heads/master@{#406033}

build/sanitizers/tsan_suppressions.cc

@@ -267,9 +267,6 @@ char kTSanDefaultSuppressions[] =
 // http://crbug.com/582274
 "race:usrsctp_close\n"
 
-// http://crbug.com/628481
-"race:IPC::SyncChannel::SyncContext::OnChannelClose\n"
-
 // End of suppressions.
 ;  // Please keep this semicolon.
 

ipc/ipc_channel_proxy.cc

@@ -324,6 +324,8 @@ void ChannelProxy::Context::OnDispatchConnected() {
   if (channel_connected_called_)
     return;
 
+  {
+    base::AutoLock l(channel_lifetime_lock_);
     if (channel_) {
       Channel::AssociatedInterfaceSupport* associated_interface_support =
           channel_->GetAssociatedInterfaceSupport();
@@ -332,6 +334,7 @@ void ChannelProxy::Context::OnDispatchConnected() {
             *associated_interface_support->GetAssociatedGroup()));
       }
     }
+  }
 
   channel_connected_called_ = true;
   if (listener_)