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"
@@ skipping 127 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 {
+#if defined(__GNUC__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wtype-limits"
+#endif

[Peter Kasting, 2014/10/29 17:08:00]

Definitely don't fix the warning this way -- the right answer is to change the
code so it doesn't produce the warning.

It's somewhat unfortunate that ICU defines all these methods as macros instead
of as functions.  I wonder if they'd ever be willing to change that.  We have
some ICU contributors on the team, you might ask them.

In the meantime, there are a couple obvious possible fixes here:

    U16_SET_CP_LIMIT(text_.c_str(), 0, index, -1);

or

    U16_SET_CP_LIMIT(text_.data(), 0, index,
                     base::checked_cast<int32_t>(text_.length()));

I'd probably do the former since it's simplest.

   DCHECK_LE(index, text_.length());
   if (index != text_.length())
     U16_SET_CP_LIMIT(text_.data(), 0, index, text_.length());
   return index;
+#if defined(__GCC__)
+#pragma GCC diagnostic pop
+#endif
 }
 
 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();
 #elif defined(OS_POSIX)
@@ skipping 655 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