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

mojo/embedder/simple_platform_support.h

Index: mojo/embedder/simple_platform_support.h
diff --git a/mojo/embedder/simple_platform_support.h b/mojo/embedder/simple_platform_support.h
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+++ b/mojo/embedder/simple_platform_support.h
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+// 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_SIMPLE_PLATFORM_SUPPORT_H_
+#define MOJO_EMBEDDER_SIMPLE_PLATFORM_SUPPORT_H_
+
+#include "base/macros.h"
+#include "mojo/embedder/platform_support.h"
+#include "mojo/system/system_impl_export.h"
+
+namespace mojo {
+namespace embedder {
+
+// A simple implementation of |PlatformSupport|, when sandboxing and
+// multiprocess support are not issues (e.g., in most tests). Note: This class
+// has no state, and different instances of |SimplePlatformSupport| are mutually
+// compatible (i.e., you don't need to use a single instance of it everywhere --
+// you may simply create one whenever/wherever you need it).
+class MOJO_SYSTEM_IMPL_EXPORT SimplePlatformSupport : public PlatformSupport {
+ public:
+  SimplePlatformSupport() {}
+  virtual ~SimplePlatformSupport() {}
+
+  virtual PlatformSharedBuffer* CreateSharedBuffer(size_t num_bytes) OVERRIDE;
+  virtual PlatformSharedBuffer* CreateSharedBufferFromHandle(
+      size_t num_bytes,
+      ScopedPlatformHandle platform_handle) OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SimplePlatformSupport);
+};
+
+}  // namespace embedder
+}  // namespace mojo
+
+#endif  // MOJO_EMBEDDER_SIMPLE_PLATFORM_SUPPORT_H_