Add NSString category for providing iOS6-style string drawing APIs.

ui/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/ios/NSString+CrStringDrawing.h"
+
+#include "base/logging.h"
+
+namespace {
+// Returns the closest pixel-aligned value higher than |value|, taking the scale
+// factor into account. At a scale of 1, equivalent to ceil().
+// TODO(lliabraa): Move this method to a common util file (crbug.com/409823).
+CGFloat alignValueToUpperPixel(CGFloat value) {
+  CGFloat scale = [[UIScreen mainScreen] scale];
+  return ceil(value * scale) / scale;
+}
+}  // namespace
+
+@implementation NSString (CrStringDrawing)
+
+- (CGSize)cr_pixelAlignedSizeWithFont:(UIFont*)font {
+  DCHECK(font) << "|font| can not be nil; it is used as a NSDictionary value";
+  NSDictionary* attributes = @{ NSFontAttributeName : font };
+  CGSize size = [self sizeWithAttributes:attributes];
+  return CGSizeMake(alignValueToUpperPixel(size.width),
+                    alignValueToUpperPixel(size.height));
+}
+
+- (CGSize)cr_sizeWithFont:(UIFont*)font {
+  if (!font)
+    return CGSizeZero;
+  NSDictionary* attributes = @{ NSFontAttributeName : font };
+  CGSize size = [self sizeWithAttributes:attributes];
+  return CGSizeMake(ceil(size.width), ceil(size.height));
+}
+
+@end