Add common data types for input method support.

ui/base/ime/composition.h

+// Copyright (c) 2011 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 UI_BASE_IME_COMPOSITION_H_
+#define UI_BASE_IME_COMPOSITION_H_
+#pragma once
+
+#include "base/string16.h"
+#include "ui/base/ime/composition_underline.h"
+#include "ui/base/range/range.h"
+
+namespace ui {
+
+// A struct represents the status of an ongoing composition.
+struct Composition {
+  void Clear();
+
+  // Content of the composition text.
+  string16 text;
+
+  // Underline information of the composition text.
+  // They must be sorted in ascending order by their start_offset and cannot be
+  // overlapped with each other.
+  CompositionUnderlines underlines;
+
+  // Selection range in the composition text. It represents the caret position
+  // if the range length is zero. Usually it's used for representing the target
+  // clause (on Windows). Gtk doesn't have such concept, so background color is
+  // usually used instead.
+  Range selection;
+};
+
+}  // namespace ui
+
+#endif  // UI_BASE_IME_COMPOSITION_H_