Reintroduce password support to NativeTextfieldViews

ui/base/text/utf16_indexing.h

+// Copyright (c) 2012 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_TEXT_UTF16_INDEXING_H_
+#define UI_BASE_TEXT_UTF16_INDEXING_H_
+#pragma once
+
+#include "base/string16.h"
+#include "ui/base/ui_export.h"
+
+namespace ui {
+
+// Returns false if s[index-1] is a high surrogate and s[index] is a low
+// surrogate, true otherwise.
+UI_EXPORT bool IsValidCodePointIndex(const string16& s, size_t index);
+
+// |UTF16IndexToOffset| returns the number of code points between |base| and
+// |pos| in the given string. |UTF16OffsetToIndex| returns the index that is
+// |offset| code points away from the given |base| index. These functions are
+// named after glib's |g_utf8_pointer_to_offset| and |g_utf8_offset_to_pointer|,
+// which perform the same function for UTF-8. As in glib, it is an error to
+// pass an |offset| that walks off the edge of the string.
+//
+// These functions attempt to deal with invalid use of UTF-16 surrogates in a
+// way that makes as much sense as possible: unpaired surrogates are treated as
+// single characters, and if an argument index points to the middle of a valid
+// surrogate pair, it is treated as though it pointed to the end of that pair.
+// The index returned by |UTF16OffsetToIndex| never points to the middle of a
+// surrogate pair.
+//
+// The following identities hold:
+//   If |s| contains no surrogate pairs, then
+//     UTF16IndexToOffset(s, base, pos) == pos - base
+//     UTF16OffsetToIndex(s, base, offset) == base + offset
+//   If |pos| does not point to the middle of a surrogate pair, then
+//     UTF16OffsetToIndex(s, base, UTF16IndexToOffset(s, base, pos)) == pos
+//   Always,
+//     UTF16IndexToOffset(s, base, UTF16OffsetToIndex(s, base, ofs)) == ofs
+//     UTF16IndexToOffset(s, i, j) == -UTF16IndexToOffset(s, j, i)
+UI_EXPORT ptrdiff_t UTF16IndexToOffset(const string16& s,
+                                       size_t base,
+                                       size_t pos);
+UI_EXPORT size_t UTF16OffsetToIndex(const string16& s,
+                                    size_t base,
+                                    ptrdiff_t offset);
+
+}  // namespace ui
+
+#endif  // UI_BASE_TEXT_UTF16_INDEXING_H_