Bring back the URLLoader from the old Mandoline network service.

content/network/net_adapters.h

Index: content/network/net_adapters.h
diff --git a/content/network/net_adapters.h b/content/network/net_adapters.h
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+// Copyright 2017 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 CONTENT_NETWORK_NET_ADAPTERS_
+#define CONTENT_NETWORK_NET_ADAPTERS_
+
+#include <stdint.h>
+
+#include "base/macros.h"
+#include "mojo/public/cpp/system/data_pipe.h"
+#include "net/base/io_buffer.h"
+
+namespace content {
+
+// These adapters are used to transfer data between a Mojo pipe and the net
+// library.
+//
+//   Mojo pipe              Data flow    Network library
+//   ----------------------------------------------------------
+//   NetToMojoPendingBuffer    <---      NetToMojoIOBuffer
+//
+// While the operation is in progress, the Mojo-side objects keep ownership
+// of the Mojo pipe, which in turn is kept alive by the IOBuffer. This allows
+// the request to potentially outlive the object managing the translation.
+// Mojo side of a Net -> Mojo copy. The buffer is allocated by Mojo.
+class NetToMojoPendingBuffer
+    : public base::RefCountedThreadSafe<NetToMojoPendingBuffer> {
+ public:
+  // Begins a two-phase write to the data pipe.
+  //
+  // On success, MOJO_RESULT_OK will be returned. The ownership of the given
+  // producer handle will be transferred to the new NetToMojoPendingBuffer that
+  // will be placed into *pending, and the size of the buffer will be in
+  // *num_bytes.
+  //
+  // On failure or MOJO_RESULT_SHOULD_WAIT, there will be no change to the
+  // handle, and *pending and *num_bytes will be unused.
+  static MojoResult BeginWrite(mojo::ScopedDataPipeProducerHandle* handle,
+                               scoped_refptr<NetToMojoPendingBuffer>* pending,
+                               uint32_t* num_bytes);
+  // Called to indicate the buffer is done being written to. Passes ownership
+  // of the pipe back to the caller.
+  mojo::ScopedDataPipeProducerHandle Complete(uint32_t num_bytes);
+  char* buffer() { return static_cast<char*>(buffer_); }
+
+ private:
+  friend class base::RefCountedThreadSafe<NetToMojoPendingBuffer>;
+  // Takes ownership of the handle.
+  NetToMojoPendingBuffer(mojo::ScopedDataPipeProducerHandle handle,
+                         void* buffer);
+  ~NetToMojoPendingBuffer();
+  mojo::ScopedDataPipeProducerHandle handle_;
+  void* buffer_;
+  DISALLOW_COPY_AND_ASSIGN(NetToMojoPendingBuffer);
+};
+
+// Net side of a Net -> Mojo copy. The data will be read from the network and
+// copied into the buffer associated with the pending mojo write.
+class NetToMojoIOBuffer : public net::WrappedIOBuffer {
+ public:
+  explicit NetToMojoIOBuffer(NetToMojoPendingBuffer* pending_buffer);
+
+ private:
+  ~NetToMojoIOBuffer() override;
+  scoped_refptr<NetToMojoPendingBuffer> pending_buffer_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_NETWORK_NET_ADAPTERS_