Reland #2: Add a short term solution to fix OSX 10.11 system font rendering problems.

Source/platform/fonts/mac/FontFamilyMatcherMacTest.mm

 // Copyright 2015 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 "config.h"
 #import "platform/fonts/mac/FontFamilyMatcherMac.h"
 
 #include <AppKit/AppKit.h>
 #include <gtest/gtest.h>
 
 #import "platform/mac/VersionUtilMac.h"
 
 @interface NSString (YosemiteAdditions)
 - (BOOL)containsString:(NSString*)string;
 @end
 
 namespace blink {
 
 void TestSystemFontContainsString(FontWeight desiredWeight, NSString* substring)
 {
     NSFont* font = MatchNSFontFamily(@"BlinkMacSystemFont", 0, desiredWeight, 11);
     EXPECT_TRUE([font.description containsString:substring]);
 }
 
 TEST(FontFamilyMatcherMacTest, YosemiteFontWeights)
 {
-    if (IsOSMavericksOrEarlier())
+    if (!IsOSYosemite())
         return;
 
     TestSystemFontContainsString(FontWeight100, @"-UltraLight");
     TestSystemFontContainsString(FontWeight200, @"-Thin");
     TestSystemFontContainsString(FontWeight300, @"-Light");
     TestSystemFontContainsString(FontWeight400, @"-Regular");
     TestSystemFontContainsString(FontWeight500, @"-Medium");
     TestSystemFontContainsString(FontWeight600, @"-Bold");
     TestSystemFontContainsString(FontWeight700, @"-Bold");
     TestSystemFontContainsString(FontWeight800, @"-Heavy");
     TestSystemFontContainsString(FontWeight900, @"-Heavy");
 }
 
 } // namespace blink