Mojo: (POSIX) Pass channel handle to child.

mojo/common/test/multiprocess_test_base.cc

Index: mojo/common/test/multiprocess_test_base.cc
diff --git a/mojo/common/test/multiprocess_test_base.cc b/mojo/common/test/multiprocess_test_base.cc
index 85aaa76514d23ccd6ced4e47b87e1664b8dfebb3..396272a4e49f3d3de42088c6b9a1e8edd89fb5fa 100644
--- a/mojo/common/test/multiprocess_test_base.cc
+++ b/mojo/common/test/multiprocess_test_base.cc
@@ -8,6 +8,7 @@
 #include "base/logging.h"
 #include "base/process/kill.h"
 #include "base/process/process_handle.h"
+// TODO(vtl): Remove build_config.h include when fully implemented on Windows.
 #include "build/build_config.h"
 
 namespace mojo {
@@ -96,9 +97,19 @@ CommandLine MultiprocessTestBase::MakeCmdLine(const std::string& procname,
 
 // static
 void MultiprocessTestBase::ChildSetup() {
-  // TODO(vtl)
-  NOTIMPLEMENTED();
+  CHECK(CommandLine::InitializedForCurrentProcess());
+// TODO(vtl): Not implemented on Windows yet.
+#if defined(OS_POSIX)
+  platform_client_channel =
+      system::PlatformClientChannel::CreateFromParentProcess(
+          *CommandLine::ForCurrentProcess());
+  CHECK(platform_client_channel.get());
+#endif
 }
 
+// static
+scoped_ptr<system::PlatformClientChannel>
+    MultiprocessTestBase::platform_client_channel;
+
 }  // namespace test
 }  // namespace mojo