[mojo] Implement data pipe using a shared buffer.

mojo/edk/system/core.cc

Index: mojo/edk/system/core.cc
diff --git a/mojo/edk/system/core.cc b/mojo/edk/system/core.cc
index 80e9815ac5f21808f7a401330ddbd90d65679a12..e37175552fb972aee56d06ddef4c2e6a82e1e38a 100644
--- a/mojo/edk/system/core.cc
+++ b/mojo/edk/system/core.cc
@@ -470,13 +470,23 @@ MojoResult Core::CreateDataPipe(
   ScopedPlatformHandle server_handle, client_handle;
 #if defined(OS_WIN)
   internal::g_broker->CreatePlatformChannelPair(&server_handle, &client_handle);
+  scoped_refptr<PlatformSharedBuffer> server_buffer =
+      internal::g_platform_support->CreateSharedBuffer(
+          validated_options.capacity_num_bytes);
 #else
   PlatformChannelPair channel_pair;
   server_handle = channel_pair.PassServerHandle();
   client_handle = channel_pair.PassClientHandle();
+  scoped_refptr<PlatformSharedBuffer> server_buffer =
+      internal::g_broker->CreateSharedBuffer(
+          validated_options.capacity_num_bytes);
 #endif
-  producer_dispatcher->Init(std::move(server_handle), nullptr, 0u);
-  consumer_dispatcher->Init(std::move(client_handle), nullptr, 0u);
+  scoped_refptr<PlatformSharedBuffer> client_buffer =
+      internal::g_platform_support->CreateSharedBufferFromHandle(
+          validated_options.capacity_num_bytes,
+          server_buffer->DuplicatePlatformHandle());
+  producer_dispatcher->Init(std::move(server_handle), server_buffer);
+  consumer_dispatcher->Init(std::move(client_handle), client_buffer);
 
   *data_pipe_producer_handle = handle_pair.first;
   *data_pipe_consumer_handle = handle_pair.second;