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

trunk/src/ports/SkFontHost_fontconfig.cpp

Index: trunk/src/ports/SkFontHost_fontconfig.cpp
===================================================================
--- trunk/src/ports/SkFontHost_fontconfig.cpp	(revision 8405)
+++ trunk/src/ports/SkFontHost_fontconfig.cpp	(working copy)
@@ -222,3 +222,12 @@
     desc->setFamilyName(this->getFamilyName());
     *isLocalStream = SkToBool(this->getLocalStream());
 }
+
+///////////////////////////////////////////////////////////////////////////////
+
+#include "SkFontMgr.h"
+
+SkFontMgr* SkFontMgr::Factory() {
+    // todo
+    return NULL;
+}