Add support for logging information about mojo messages retrieved by the mojo debugger

mojo/spy/common.h

Index: mojo/spy/common.h
diff --git a/mojo/spy/common.h b/mojo/spy/common.h
new file mode 100644
index 0000000000000000000000000000000000000000..f39f28393900276f0fa7c199d20bbe7ad7a4b8d3
--- /dev/null
+++ b/mojo/spy/common.h
@@ -0,0 +1,43 @@
+// Copyright 2014 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.
+
+#ifndef MOJO_SPY_COMMON_H_
+#define MOJO_SPY_COMMON_H_
+
+#include <stdint.h>
+
+namespace mojo {
+
+#pragma pack(push, 1)
+
+// Mojo message header structures. These are based off the Mojo spec.
+
+enum {
+  kMessageExpectsResponse = 1 << 0,
+  kMessageIsResponse      = 1 << 1
+};
+
+struct MojoCommonHeader {
+  uint32_t num_bytes;
+  uint32_t num_fields;
+};
+
+struct MojoMessageHeader : public MojoCommonHeader {
+  uint32_t name;
+  uint32_t flags;
+};
+
+struct MojoRequestHeader : public MojoMessageHeader {
+  uint64_t request_id;
+};
+
+struct MojoMessageData  {
+  MojoRequestHeader header;
+};
+
+#pragma pack(pop)
+
+}  // namespace mojo
+
+#endif  // MOJO_SPY_COMMON_H_