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

trunk/src/ports/SkFontHost_linux.cpp

Index: trunk/src/ports/SkFontHost_linux.cpp
===================================================================
--- trunk/src/ports/SkFontHost_linux.cpp	(revision 8405)
+++ trunk/src/ports/SkFontHost_linux.cpp	(working copy)
@@ -517,3 +517,12 @@
     SkAutoTUnref<SkStream> stream(SkStream::NewFromFile(path));
     return stream.get() ? CreateTypefaceFromStream(stream) : NULL;
 }
+
+///////////////////////////////////////////////////////////////////////////////
+
+#include "SkFontMgr.h"
+
+SkFontMgr* SkFontMgr::Factory() {
+    // todo
+    return NULL;
+}