Add a Mojo EDK for Chrome that uses one OS pipe per message pipe.

mojo/edk/system/platform_handle_dispatcher.h

Index: mojo/edk/system/platform_handle_dispatcher.h
diff --git a/third_party/mojo/src/mojo/edk/system/platform_handle_dispatcher.h b/mojo/edk/system/platform_handle_dispatcher.h
similarity index 87%
copy from third_party/mojo/src/mojo/edk/system/platform_handle_dispatcher.h
copy to mojo/edk/system/platform_handle_dispatcher.h
index 8e8cf6904d96450fb8f6223cabcc78996155d9fe..c445ba92ba11e4af2185b9ba8c6c7840a555c175 100644
--- a/third_party/mojo/src/mojo/edk/system/platform_handle_dispatcher.h
+++ b/mojo/edk/system/platform_handle_dispatcher.h
@@ -32,7 +32,6 @@ class MOJO_SYSTEM_IMPL_EXPORT PlatformHandleDispatcher final
   // The "opposite" of |SerializeAndClose()|. (Typically this is called by
   // |Dispatcher::Deserialize()|.)
   static scoped_refptr<PlatformHandleDispatcher> Deserialize(
-      Channel* channel,
       const void* source,
       size_t size,
       embedder::PlatformHandleVector* platform_handles);
@@ -46,18 +45,14 @@ class MOJO_SYSTEM_IMPL_EXPORT PlatformHandleDispatcher final
   void CloseImplNoLock() override;
   scoped_refptr<Dispatcher> CreateEquivalentDispatcherAndCloseImplNoLock()
       override;
-  void StartSerializeImplNoLock(Channel* channel,
-                                size_t* max_size,
-                                size_t* max_platform_handles) override
-      MOJO_NOT_THREAD_SAFE;
+  void StartSerializeImplNoLock(size_t* max_size,
+                                size_t* max_platform_handles) override;
   bool EndSerializeAndCloseImplNoLock(
-      Channel* channel,
       void* destination,
       size_t* actual_size,
-      embedder::PlatformHandleVector* platform_handles) override
-      MOJO_NOT_THREAD_SAFE;
+      embedder::PlatformHandleVector* platform_handles) override;
 
-  embedder::ScopedPlatformHandle platform_handle_ MOJO_GUARDED_BY(mutex());
+  embedder::ScopedPlatformHandle platform_handle_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(PlatformHandleDispatcher);
 };