Implement SkEmptyFontMgr::onLegacyCreateTypeface and make pure virtual.

src/core/SkFontHost.cpp

Index: src/core/SkFontHost.cpp
===================================================================
--- src/core/SkFontHost.cpp	(revision 10850)
+++ src/core/SkFontHost.cpp	(working copy)
@@ -126,6 +126,9 @@
     virtual SkTypeface* onCreateFromFile(const char[], int) SK_OVERRIDE {
         return NULL;
     }
+    virtual SkTypeface* onLegacyCreateTypeface(const char [], unsigned) SK_OVERRIDE {
+        return NULL;
+    }
 };
 
 static SkFontStyleSet* emptyOnNull(SkFontStyleSet* fsset) {
@@ -187,12 +190,6 @@
     return this->onLegacyCreateTypeface(familyName, styleBits);
 }
 
-SkTypeface* SkFontMgr::onLegacyCreateTypeface(const char familyName[],
-                                              unsigned styleBits) {
-    SkASSERT(!"unimplemented");
-    return NULL;
-}
-
 SkFontMgr* SkFontMgr::RefDefault() {
     static SkFontMgr* gFM;
     if (NULL == gFM) {