IPC: Remove unnecessary conversions of BrokerableAttachment.

BrokerableAttachments are typically stored and passed around in a scoped_refptr.
There were several locations where they were being unnecessarily converted to a
raw pointer. This was probably responsible for a non-deterministic crash on GPU
bots (https://code.google.com/p/chromium/issues/detail?id=535711#c28), although
I haven't been able to reproduce the problem locally.

BUG=535711

Review URL: https://codereview.chromium.org/1414503009

Cr-Commit-Position: refs/heads/master@{#356968}
diff --git a/ipc/attachment_broker_mac_unittest.cc b/ipc/attachment_broker_mac_unittest.cc
index 4d1f5bc..e3062b58 100644
--- a/ipc/attachment_broker_mac_unittest.cc
+++ b/ipc/attachment_broker_mac_unittest.cc
@@ -264,8 +264,9 @@
  public:
   MockBroker() {}
   ~MockBroker() override {}
-  bool SendAttachmentToProcess(IPC::BrokerableAttachment* attachment,
-                               base::ProcessId destination_process) override {
+  bool SendAttachmentToProcess(
+      const scoped_refptr<IPC::BrokerableAttachment>& attachment,
+      base::ProcessId destination_process) override {
     return IPC::AttachmentBrokerUnprivilegedMac::SendAttachmentToProcess(
         attachment, base::Process::Current().Pid());
   }