CrStringDrawing cleanup: added braces to index arithmetics.

ui/gfx/ios/NSString+CrStringDrawing.mm

 // Copyright 2014 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.
 
 #import "ui/gfx/ios/NSString+CrStringDrawing.h"
 
 #include "base/logging.h"
 #include "ui/gfx/ios/uikit_util.h"
 
 @implementation NSString (CrStringDrawing)
@@ skipping 24 matching lines @@
   NSDictionary* attributes = @{ NSFontAttributeName : font };
   CGSize size = [self sizeWithAttributes:attributes];
   return CGSizeMake(ceil(size.width), ceil(size.height));
 }
 
 - (NSString*)cr_stringByCuttingToIndex:(NSUInteger)index {
   if (index == 0)
     return @"";
   if (index >= [self length])
     return [[self retain] autorelease];
-  return [[self substringToIndex:index - 1] stringByAppendingString:@"…"];
+  return [[self substringToIndex:(index - 1)] stringByAppendingString:@"…"];
 }
 
 - (NSString*)cr_stringByElidingToFitSize:(CGSize)bounds {
   CGSize sizeForGuess = CGSizeMake(bounds.width, CGFLOAT_MAX);
   // Use binary search on the string's length.
   size_t lo = 0;
   size_t hi = [self length];
   size_t guess = 0;
   for (guess = (lo + hi) / 2; lo < hi; guess = (lo + hi) / 2) {
     NSString* tempString = [self cr_stringByCuttingToIndex:guess];
     UIFont* font = [UIFont systemFontOfSize:[UIFont labelFontSize]];
     CGSize sizeGuess =
         [tempString cr_boundingSizeWithSize:sizeForGuess font:font];
     if (sizeGuess.height > bounds.height) {
       hi = guess - 1;
       if (hi < lo)
         hi = lo;
     } else {
       lo = guess + 1;
     }
   }
   return [self cr_stringByCuttingToIndex:lo];
 }
 
 @end