Add last resort to fallback chain in FontFallbackList::primaryFontData

Source/platform/fonts/FontFallbackList.cpp

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 96 matching lines @@
 }
 
 const FontData* FontFallbackList::primaryFontData(const FontDescription& fontDescription) const
 {
     bool shouldLoadCustomFont = true;
 
     for (unsigned fontIndex = 0; ; ++fontIndex) {
         const FontData* fontData = fontDataAt(fontDescription, fontIndex);
         if (!fontData) {
             // All fonts are custom fonts and are loading. Return the first FontData.
-            // FIXME: Correct fallback to the default font.
-            return fontDataAt(fontDescription, 0);
+            fontData = fontDataAt(fontDescription, 0);
+            if (!fontData)
+                fontData = FontCache::fontCache()->getLastResortFallbackFont(fontDescription).get();
+            ASSERT(fontData);
+            return fontData;
         }
 
         if (fontData->isSegmented() && !toSegmentedFontData(fontData)->containsCharacter(' '))
             continue;
 
         // When a custom font is loading, we should use the correct fallback font to layout the text.
         // Here skip the temporary font for the loading custom font which may not act as the correct fallback font.
         if (!fontData->isLoadingFallback())
             return fontData;
 
@@ skipping 67 matching lines @@
     RefPtr<FontData> result = getFontData(fontDescription, m_familyIndex);
     if (result) {
         m_fontList.append(result);
         if (result->isLoading())
             m_loadingCustomFonts = true;
     }
     return result.get();
 }
 
 }