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

Source/platform/mac/VersionUtilMac.mm

Index: Source/platform/mac/VersionUtilMac.mm
diff --git a/Source/platform/mac/VersionUtilMac.mm b/Source/platform/mac/VersionUtilMac.mm
index 2eda3c825afc0bdfa3a197082aebaf72f234016c..abb5f7a2239ba23cb88b506677517addf7bab7b7 100644
--- a/Source/platform/mac/VersionUtilMac.mm
+++ b/Source/platform/mac/VersionUtilMac.mm
@@ -60,6 +60,8 @@ int MacOSXMinorVersion()
 enum {
     LION_MINOR_VERSION = 7,
     MAVERICKS_MINOR_VERSION = 9,
+    YOSEMITE_MINOR_VERSION = 10,
+    EL_CAPITAN_MINOR_VERSION = 11,
 };
 
 } // namespace
@@ -81,4 +83,14 @@ bool IsOSMavericks()
     return MacOSXMinorVersion() == MAVERICKS_MINOR_VERSION;
 }
 
+bool IsOSYosemite()
+{
+    return MacOSXMinorVersion() == YOSEMITE_MINOR_VERSION;
+}
+
+bool IsOSElCapitan()
+{
+    return MacOSXMinorVersion() == EL_CAPITAN_MINOR_VERSION;
+}
+
 } // namespace blink