Update iOS deployment target to 7.0

ui/gfx/text_utils_ios.mm

Index: ui/gfx/text_utils_ios.mm
diff --git a/ui/gfx/text_utils_ios.mm b/ui/gfx/text_utils_ios.mm
index 56c01df7f554371671427b60dde2480ee4efaf2a..304f9ff67bca43bcb2cd35b4f2cbd71496510b9e 100644
--- a/ui/gfx/text_utils_ios.mm
+++ b/ui/gfx/text_utils_ios.mm
@@ -20,7 +20,8 @@ int GetStringWidth(const base::string16& text, const FontList& font_list) {
 float GetStringWidthF(const base::string16& text, const FontList& font_list) {
   NSString* ns_text = base::SysUTF16ToNSString(text);
   NativeFont native_font = font_list.GetPrimaryFont().GetNativeFont();
-  return [ns_text sizeWithFont:native_font].width;
+  NSDictionary* attributes = @{ NSFontAttributeName : native_font };
+  return std::ceil([ns_text sizeWithAttributes:attributes].width);
 }
 
 }  // namespace gfx