Subject .mm files to the header sorting presubmit

ui/gfx/platform_font_mac_unittest.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 <Cocoa/Cocoa.h>
 
+#include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/font.h"
-#include "testing/gtest/include/gtest/gtest.h"
 
 TEST(PlatformFontMacTest, DeriveFont) {
   // Use a base font that support all traits.
   gfx::Font base_font("Helvetica", 13);
 
   // Bold
   gfx::Font bold_font(base_font.Derive(0, gfx::Font::BOLD));
   NSFontTraitMask traits = [[NSFontManager sharedFontManager]
       traitsOfFont:bold_font.GetNativeFont()];
   EXPECT_EQ(NSBoldFontMask, traits);
@@ skipping 28 matching lines @@
   EXPECT_EQ(14, italic_font.GetFontSize());
   EXPECT_EQ("Helvetica", italic_font.GetFontName());
   EXPECT_EQ(gfx::Font::ITALIC, italic_font.GetStyle());
 
   gfx::Font bold_italic_font(
       [NSFont fontWithName:@"Helvetica-BoldOblique" size:14]);
   EXPECT_EQ(14, bold_italic_font.GetFontSize());
   EXPECT_EQ("Helvetica", bold_italic_font.GetFontName());
   EXPECT_EQ(gfx::Font::BOLD | gfx::Font::ITALIC, bold_italic_font.GetStyle());
 }