Make mojo::internal::Buffer a non-virtual class.

mojo/public/cpp/bindings/lib/fixed_buffer.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_PUBLIC_CPP_BINDINGS_LIB_FIXED_BUFFER_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_FIXED_BUFFER_H_
 
 #include <stddef.h>
 
 #include "base/macros.h"
 #include "mojo/public/cpp/bindings/lib/buffer.h"
 
 namespace mojo {
 namespace internal {
 
-// FixedBuffer provides a simple way to allocate objects within a fixed chunk
-// of memory. Objects are allocated by calling the |Allocate| method, which
-// extends the buffer accordingly. Objects allocated in this way are not freed
-// explicitly. Instead, they remain valid so long as the FixedBuffer remains
-// valid.  The Leak method may be used to steal the underlying memory from the
-// FixedBuffer.
-//
-// Typical usage:
-//
-//   {
-//     FixedBuffer buf(8 + 8);
-//
-//     int* a = static_cast<int*>(buf->Allocate(sizeof(int)));
-//     *a = 2;
-//
-//     double* b = static_cast<double*>(buf->Allocate(sizeof(double)));
-//     *b = 3.14f;
-//
-//     void* data = buf.Leak();
-//     Process(data);
-//
-//     free(data);
-//   }
-
-class FixedBuffer : public Buffer {
- public:
-  FixedBuffer();
-
-  // |size| should be aligned using internal::Align.
-  void Initialize(void* memory, size_t size);
-
-  size_t size() const { return size_; }
-
-  // Grows the buffer by |num_bytes| and returns a pointer to the start of the
-  // addition. The resulting address is 8-byte aligned, and the content of the
-  // memory is zero-filled.
-  void* Allocate(size_t num_bytes) override;
-
- protected:
-  char* ptr_;
-  size_t cursor_;
-  size_t size_;
-
-  DISALLOW_COPY_AND_ASSIGN(FixedBuffer);
-};
-
-class FixedBufferForTesting : public FixedBuffer {
+// FixedBufferForTesting owns its buffer. The Leak method may be used to steal
+// the underlying memory.
+class FixedBufferForTesting : public Buffer {
  public:
   explicit FixedBufferForTesting(size_t size);
-  ~FixedBufferForTesting() override;
+  ~FixedBufferForTesting();
 
   // Returns the internal memory owned by the Buffer to the caller. The Buffer
   // relinquishes its pointer, effectively resetting the state of the Buffer
   // and leaving the caller responsible for freeing the returned memory address
   // when no longer needed.
   void* Leak();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FixedBufferForTesting);
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_FIXED_BUFFER_H_