add dummpy SkFontMgr::Factory() impl to font backends, so we can start testing it

trunk/src/ports/SkFontHost_none.cpp

Index: trunk/src/ports/SkFontHost_none.cpp
===================================================================
--- trunk/src/ports/SkFontHost_none.cpp	(revision 8405)
+++ trunk/src/ports/SkFontHost_none.cpp	(working copy)
@@ -26,3 +26,12 @@
     SkDEBUGFAIL("SkFontHost::CreateTypefaceFromFile unimplemented");
     return NULL;
 }
+
+///////////////////////////////////////////////////////////////////////////////
+
+#include "SkFontMgr.h"
+
+SkFontMgr* SkFontMgr::Factory() {
+    // todo
+    return NULL;
+}