Fix a 'type-limits' warning in StringSlicer::FindValidBoundaryAfter

ui/gfx/text_elider.cc

 // 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.
 //
 // This file implements utility functions for eliding and formatting UI text.
 //
 // Note that several of the functions declared in text_elider.h are implemented
 // in this file using helper classes in an unnamed namespace.
 
 #include "ui/gfx/text_elider.h"
 
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "base/i18n/break_iterator.h"
 #include "base/i18n/char_iterator.h"
 #include "base/i18n/rtl.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/numerics/safe_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "third_party/icu/source/common/unicode/rbbi.h"
 #include "third_party/icu/source/common/unicode/uloc.h"
 #include "ui/gfx/font_list.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/render_text.h"
 #include "ui/gfx/text_utils.h"
@@ skipping 109 matching lines @@
 
 size_t StringSlicer::FindValidBoundaryBefore(size_t index) const {
   DCHECK_LE(index, text_.length());
   if (index != text_.length())
     U16_SET_CP_START(text_.data(), 0, index);
   return index;
 }
 
 size_t StringSlicer::FindValidBoundaryAfter(size_t index) const {
   DCHECK_LE(index, text_.length());
-  if (index != text_.length())
-    U16_SET_CP_LIMIT(text_.data(), 0, index, text_.length());
+  if (index != text_.length()) {
+    int32_t text_index = base::checked_cast<int32_t>(index);
+    int32_t text_length = base::checked_cast<int32_t>(text_.length());
+    U16_SET_CP_LIMIT(text_.data(), 0, text_index, text_length);
+    index = base::checked_cast<size_t>(text_index);

[Peter Kasting, 2014/10/29 19:17:26]

How about this:

  if (index == text_.length())
    return index;
  int32_t text_index = ...
  ...
  return static_cast<size_t>(text_index);

It should be OK to use a static_cast in the return statement since
text_.length() successfully checked_casted to an int32_t.  And this
restructuring of the code makes it harder for someone in the future to break the
code by not returning the updated value.

+  }
   return index;
 }
 
 base::string16 ElideFilename(const base::FilePath& filename,
                              const FontList& font_list,
                              float available_pixel_width) {
 #if defined(OS_WIN)
   base::string16 filename_utf16 = filename.value();
   base::string16 extension = filename.Extension();
   base::string16 rootname = filename.BaseName().RemoveExtension().value();
@@ skipping 656 matching lines @@
     index = char_iterator.getIndex();
   } else {
     // String has leading whitespace, return the elide string.
     return kElideString;
   }
 
   return string.substr(0, index) + kElideString;
 }
 
 }  // namespace gfx