Mojo: Add embedder::PlatformSupport and a simple implementation (and a bit of plumbing).

mojo/embedder/platform_support.h

+// 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_EMBEDDER_PLATFORM_SUPPORT_H_
+#define MOJO_EMBEDDER_PLATFORM_SUPPORT_H_
+
+#include <stddef.h>
+
+#include "base/macros.h"
+#include "mojo/embedder/scoped_platform_handle.h"
+#include "mojo/system/system_impl_export.h"
+
+namespace mojo {
+namespace embedder {
+
+class PlatformSharedBuffer;
+
+// This class is provided by the embedder to implement (typically
+// platform-dependent) things needed by the Mojo system implementation.
+class MOJO_SYSTEM_IMPL_EXPORT PlatformSupport {
+ public:
+  virtual ~PlatformSupport() {}

[darin (slow to review), 2014/08/14 23:30:57]

should this destructor be protected as well? based on what you have so far in
this CL, it looks like the system will not take ownership over this pointer,
right?

[viettrungluu, 2014/08/15 00:25:27]

Probably when I add one to Core, I'll make Core own it (to avoid having to say
that the caller must ensure that the PlatformSupport outlives Core, etc.).

(At least that's my current thinking. I'm not sure if it's entirely right.)

+
+  virtual PlatformSharedBuffer* CreateSharedBuffer(size_t num_bytes) = 0;
+  virtual PlatformSharedBuffer* CreateSharedBufferFromHandle(
+      size_t num_bytes,
+      ScopedPlatformHandle platform_handle) = 0;
+
+ protected:
+  PlatformSupport() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PlatformSupport);
+};
+
+}  // namespace embedder
+}  // namespace mojo
+
+#endif  // MOJO_EMBEDDER_PLATFORM_SUPPORT_H_