[ui/ios] Add helper methods for getting the bounding size of some text.

ui/ios/NSString+CrStringDrawing.mm

Index: ui/ios/NSString+CrStringDrawing.mm
diff --git a/ui/ios/NSString+CrStringDrawing.mm b/ui/ios/NSString+CrStringDrawing.mm
index 214b0c19102cc65d4f822ba4762fe00dac936aaf..e9274e9849979fabb6b81e422603e5ebc6b80d83 100644
--- a/ui/ios/NSString+CrStringDrawing.mm
+++ b/ui/ios/NSString+CrStringDrawing.mm
@@ -9,6 +9,20 @@
 
 @implementation NSString (CrStringDrawing)
 
+- (CGRect)cr_boundingRectWithSize:(CGSize)size
+                             font:(UIFont*)font {
+  NSDictionary* attributes = font ? @{NSFontAttributeName: font} : @{};
+  return [self boundingRectWithSize:size
+                            options:NSStringDrawingUsesLineFragmentOrigin
+                         attributes:attributes
+                            context:nil];
+}
+
+- (CGSize)cr_boundingSizeWithSize:(CGSize)size
+                             font:(UIFont*)font {
+  return [self cr_boundingRectWithSize:size font:font].size;
+}
+
 - (CGSize)cr_pixelAlignedSizeWithFont:(UIFont*)font {
   DCHECK(font) << "|font| can not be nil; it is used as a NSDictionary value";
   NSDictionary* attributes = @{ NSFontAttributeName : font };