ipc: Use a global for the process's attachment broker.

content/gpu/gpu_child_thread.cc

Index: content/gpu/gpu_child_thread.cc
diff --git a/content/gpu/gpu_child_thread.cc b/content/gpu/gpu_child_thread.cc
index 7cb56a7671566840f68b12c52c34dad1ed65e1b3..c6c1e3137bd79e7b03e39f3a5f019c5d6ce3e3f4 100644
--- a/content/gpu/gpu_child_thread.cc
+++ b/content/gpu/gpu_child_thread.cc
@@ -261,7 +261,7 @@ void GpuChildThread::OnInitialize() {
       channel(), watchdog_thread_.get(),
       base::ThreadTaskRunnerHandle::Get().get(),
       ChildProcess::current()->io_task_runner(),
-      ChildProcess::current()->GetShutDownEvent(), GetAttachmentBroker(),
+      ChildProcess::current()->GetShutDownEvent(),
       sync_point_manager_, gpu_memory_buffer_factory_));
 
 #if defined(USE_OZONE)