Introduce ForwardsTextBuffer and BackwardsTextBuffer

third_party/WebKit/Source/core/editing/iterators/ForwardsTextBuffer.cpp

Index: third_party/WebKit/Source/core/editing/iterators/ForwardsTextBuffer.cpp
diff --git a/third_party/WebKit/Source/core/editing/iterators/ForwardsTextBuffer.cpp b/third_party/WebKit/Source/core/editing/iterators/ForwardsTextBuffer.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..9bc426895f169b4e0a6a7235d610bd4ed3a99233
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/iterators/ForwardsTextBuffer.cpp
@@ -0,0 +1,20 @@
+// Copyright 2016 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.
+
+#include "core/editing/iterators/ForwardsTextBuffer.h"
+
+namespace blink {
+
+const UChar* ForwardsTextBuffer::data() const
+{
+    return bufferBegin();
+}
+
+UChar* ForwardsTextBuffer::calcDestination(size_t length)
+{
+    ASSERT(size() + length <= capacity());
+    return bufferBegin() + size();
+}
+
+} // namespace blink