Add DirectWrite flag and plumb it through to Blink

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 82aff475da384fce75853adaa0d88875e7417710..01e72f23c7754738b1e9ccc3c3fbf5a2b93cb02d 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -458,6 +458,9 @@ const char kEnableHighDpiCompositingForFixedPosition[] =
      "enable-high-dpi-fixed-position-compositing";
 
 #if defined(OS_WIN)
+// Enables the DirectWrite font rendering system on windows.
+const char kEnableDirectWrite[]             = "enable-direct-write";
+
 // Use high resolution timers for TimeTicks.
 const char kEnableHighResolutionTime[]      = "enable-high-resolution-time";
 #endif