[cloud-print] Fix service utility process launch

Fixes a bug which breaks sandboxed service utility process launching.
The launcher was invalidating the child process's Mojo channel handle
before launch.

Bug: 882158
Change-Id: I406bc3adcf9be2e74dda87f536151b4f05ac3319
Reviewed-on: https://chromium-review.googlesource.com/1220266Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Ken Rockot <rockot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590401}

chrome/service/service_utility_process_host.cc

@@ -428,8 +428,6 @@ bool ServiceUtilityProcessHost::Launch(base::CommandLine* cmd_line,
 
   if (sandbox) {
     mojo::PlatformChannel channel;
-    mojo::PlatformChannelEndpoint client_endpoint =
-        channel.TakeRemoteEndpoint();
     base::HandlesToInheritVector handles;
     channel.PrepareToPassRemoteEndpoint(&handles, cmd_line);