Add `chunk` segmented data library.

common/chunkstream/chunk.go

Index: common/chunkstream/chunk.go
diff --git a/common/chunkstream/chunk.go b/common/chunkstream/chunk.go
new file mode 100644
index 0000000000000000000000000000000000000000..3610e514c05af9184f0860ad106ee3f62b335fb2
--- /dev/null
+++ b/common/chunkstream/chunk.go
@@ -0,0 +1,19 @@
+// Copyright 2015 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.
+
+package chunkstream
+
+// Chunk wraps a fixed-size byte buffer. It is the primary interface used by
+// the chunk library.
+//
+// A Chunk reference should be released once the user is finished with it. After
+// being released, it may no longer be accessed.
+type Chunk interface {
+	// Bytes returns the underlying byte slice contained by this Chunk.
+	Bytes() []byte
+
+	// Release releases the Chunk. After being released, a Chunk's methods may no
+	// longer be used.
+	Release()
+}