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..3ae9be9be8bc4d5dab7f2bb62e52c34c403dcec8 100644
--- a/third_party/WebKit/public/web/win/WebFontRendering.h
+++ b/third_party/WebKit/public/web/win/WebFontRendering.h
@@ -7,16 +7,16 @@
 
 #include "public/platform/WebCommon.h"
 #include <SkFontHost.h>

[tfarina, 2016/01/21 22:45:27]

shouldn't we include this by its full path now? third_party/skia/include/...

[Ilya Kulshin, 2016/01/27 22:07:25]

Done.

+#include <SkFontMgr.h>

[bungeman-chromium, 2016/01/21 22:25:09]

Not sure what the current policy is on forward declarations, but I think this
can just be

class SkFontMgr;

[tfarina, 2016/01/21 22:45:27]

Yes, please. Blink is already too slow to compile!

[Ilya Kulshin, 2016/01/27 22:07:25]

Done.

 
 class SkTypeface;
-struct IDWriteFactory;
 
 namespace blink {
 
 class WebFontRendering {
 public:
     BLINK_EXPORT static void setUseDirectWrite(bool);
-    BLINK_EXPORT static void setDirectWriteFactory(IDWriteFactory*);
+    BLINK_EXPORT static void setSkiaFontManager(SkFontMgr*);
     BLINK_EXPORT static void setDeviceScaleFactor(float);
     BLINK_EXPORT static void setUseSubpixelPositioning(bool);
     BLINK_EXPORT static void addSideloadedFontForTesting(SkTypeface*);