Add plumbing in blink to allow overriding the default font collection.

third_party/WebKit/public/web/win/WebFontRendering.h

Index: third_party/WebKit/public/web/win/WebFontRendering.h
diff --git a/third_party/WebKit/public/web/win/WebFontRendering.h b/third_party/WebKit/public/web/win/WebFontRendering.h
index 5c7c3836d7c3e7f6d282b4fc8bb9029c49cce3d1..255284a4273a1dd2641a236ad0efebd49899ebf0 100644
--- a/third_party/WebKit/public/web/win/WebFontRendering.h
+++ b/third_party/WebKit/public/web/win/WebFontRendering.h
@@ -6,7 +6,9 @@
 #define WebFontRendering_h
 
 #include "public/platform/WebCommon.h"
+#include <RefPtr.h>
 #include <SkFontHost.h>
+#include <SkFontMgr.h>
 
 class SkTypeface;
 struct IDWriteFactory;
@@ -17,6 +19,7 @@ class WebFontRendering {
 public:
     BLINK_EXPORT static void setUseDirectWrite(bool);
     BLINK_EXPORT static void setDirectWriteFactory(IDWriteFactory*);
+    BLINK_EXPORT static void setSkiaFontManager(const skia::RefPtr<SkFontMgr>&);
     BLINK_EXPORT static void setDeviceScaleFactor(float);
     BLINK_EXPORT static void setUseSubpixelPositioning(bool);
     BLINK_EXPORT static void addSideloadedFontForTesting(SkTypeface*);