ipc: Move //crypto dependency into a Windows-only file.

//ipc only depends on //crypto on Windows. GN checks #includes against
dependencies, but isn't able to evaluate preprocessor conditionals. This causes
problems. In https://codereview.chromium.org/1321253011/, the dependency was
moved into several other files, but this also changed the public interface of
BrokerableAttachment::AttachmentId in an undesirable manner. Instead, this CL
makes the new file brokerable_attachment_win.cc to include the the crypto
dependency.

BUG=

Review URL: https://codereview.chromium.org/1345633002

Cr-Commit-Position: refs/heads/master@{#348923}

1 files changed, 18 insertions, 0 deletions

diff --git a/ipc/brokerable_attachment_win.cc b/ipc/brokerable_attachment_win.cc
new file mode 100644
index 0000000..6b567e6
--- /dev/null
+++ b/ipc/brokerable_attachment_win.cc
@@ -0,0 +1,18 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ipc/brokerable_attachment.h"
+
+#include "crypto/random.h"
+
+namespace IPC {
+
+BrokerableAttachment::AttachmentId::AttachmentId() {
+  // In order to prevent mutually untrusted processes from stealing resources
+  // from one another, the nonce must be secret. This generates a 128-bit,
+  // cryptographicaly-strong random number.
+  crypto::RandBytes(nonce, BrokerableAttachment::kNonceSize);
+}
+
+}  // namespace IPC