Fix font height on Mac with Helvetica Neue at size 16 (ResourceBundle::MediumFont)

ui/gfx/platform_font_mac.mm

 // 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.
 
 #include "ui/gfx/platform_font_mac.h"
 
 #include <Cocoa/Cocoa.h>
 
 #include "base/basictypes.h"
 #include "base/mac/scoped_nsobject.h"
@@ skipping 148 matching lines @@
   if (!font) {
     // This object was constructed from a font name that doesn't correspond to
     // an actual font. Don't waste time working out metrics.
     height_ = 0;
     ascent_ = 0;
     cap_height_ = 0;
     average_width_ = 0;
     return;
   }
 
-  base::scoped_nsobject<NSLayoutManager> layout_manager(
-      [[NSLayoutManager alloc] init]);
-  height_ = SkScalarCeilToInt([layout_manager defaultLineHeightForFont:font]);
-  ascent_ = SkScalarCeilToInt([font ascender]);
-  cap_height_ = SkScalarCeilToInt([font capHeight]);
+  ascent_ = ceil([font ascender]);
+  cap_height_ = ceil([font capHeight]);
+
+  // PlatformFontMac once used -[NSLayoutManager defaultLineHeightForFont:] to
+  // initialize |height_|. However, it has a silly rounding bug. Essentially, it
+  // gives round(ascent) + round(descent). E.g. Helvetica Neue at size 16 gives
+  // ascent=15.4634, descent=3.38208 -> 15 + 3 = 18. When the height should be
+  // at least 19. According to the OpenType specification, these values should
+  // simply be added, so do that. Note this uses the already-rounded |ascent_|
+  // to ensure GetBaseline() + descender fits within GetHeight() during layout.
+  height_ = ceil(ascent_ + std::abs([font descender]) + [font leading]);
+
   average_width_ =
       NSWidth([font boundingRectForGlyph:[font glyphWithName:@"x"]]);
 
   FontRenderParamsQuery query;
   query.families.push_back(font_name_);
   query.pixel_size = font_size_;
   query.style = font_style_;
   render_params_ = gfx::GetFontRenderParams(query, NULL);
 }
 
@@ skipping 10 matching lines @@
   return new PlatformFontMac(native_font);
 }
 
 // static
 PlatformFont* PlatformFont::CreateFromNameAndSize(const std::string& font_name,
                                                   int font_size) {
   return new PlatformFontMac(font_name, font_size);
 }
 
 }  // namespace gfx