Add an empty typeface as a default-default.

src/core/SkTypeface.cpp

Index: src/core/SkTypeface.cpp
===================================================================
--- src/core/SkTypeface.cpp	(revision 10850)
+++ src/core/SkTypeface.cpp	(working copy)
@@ -36,6 +36,35 @@
 
 ///////////////////////////////////////////////////////////////////////////////
 
+class SkEmptyTypeface : public SkTypeface {
+public:
+    SkEmptyTypeface() : SkTypeface(SkTypeface::kNormal, 0, true) { }
+protected:
+    virtual SkStream* onOpenStream(int* ttcIndex) const SK_OVERRIDE { return NULL; }
+    virtual SkScalerContext* onCreateScalerContext(const SkDescriptor*) const SK_OVERRIDE {
+        return NULL;
+    }
+    virtual void onFilterRec(SkScalerContextRec*) const SK_OVERRIDE { }
+    virtual SkAdvancedTypefaceMetrics* onGetAdvancedTypefaceMetrics(
+                                SkAdvancedTypefaceMetrics::PerGlyphInfo,
+                                const uint32_t*, uint32_t) const SK_OVERRIDE { return NULL; }
+    virtual void onGetFontDescriptor(SkFontDescriptor*, bool*) const SK_OVERRIDE { }
+    virtual int onCountGlyphs() const SK_OVERRIDE { return 0; };
+    virtual int onGetUPEM() const SK_OVERRIDE { return 0; };
+    class EmptyLocalizedStrings : public SkTypeface::LocalizedStrings {
+    public:
+        virtual bool next(SkTypeface::LocalizedString*) SK_OVERRIDE { return false; }
+    };
+    virtual SkTypeface::LocalizedStrings* onCreateFamilyNameIterator() const SK_OVERRIDE {
+        return SkNEW(EmptyLocalizedStrings);
+    };
+    virtual int onGetTableTags(SkFontTableTag tags[]) const SK_OVERRIDE { return 0; }
+    virtual size_t onGetTableData(SkFontTableTag, size_t, size_t, void*) const SK_OVERRIDE {
+        return 0;
+    }
+    virtual SkTypeface* onRefMatchingStyle(Style) const SK_OVERRIDE { return NULL; }
+};
+
 SkTypeface* SkTypeface::GetDefaultTypeface(Style style) {
     // we keep a reference to this guy for all time, since if we return its
     // fontID, the font cache may later on ask to resolve that back into a
@@ -48,9 +77,12 @@
     style = (Style)(style & 0x03);
 
     if (NULL == gDefaultTypefaces[style]) {
-        gDefaultTypefaces[style] =
-        SkFontHost::CreateTypeface(NULL, NULL, style);
+        gDefaultTypefaces[style] = SkFontHost::CreateTypeface(NULL, NULL, style);
     }
+    if (NULL == gDefaultTypefaces[style]) {
+        gDefaultTypefaces[style] = SkNEW(SkEmptyTypeface);
+    }
+
     return gDefaultTypefaces[style];
 }