Fix font instantiation assertion failure on session restore

Source/platform/fonts/skia/FontCacheSkia.cpp

 /*
  * Copyright (c) 2006, 2007, 2008, 2009 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 160 matching lines @@
         // TODO(dro): crbug.com/381620 Use creationParams.ttcIndex() after
         // https://code.google.com/p/skia/issues/detail?id=1186 gets fixed.
         SkTypeface* typeface = nullptr;
         if (blink::Platform::current()->sandboxSupport())
             typeface = SkTypeface::CreateFromStream(streamForFontconfigInterfaceId(creationParams.fontconfigInterfaceId()));
         else
             typeface = SkTypeface::CreateFromFile(creationParams.filename().data());
 
         if (typeface)
             return adoptRef(typeface);
+        else
+            return nullptr;
     }
 #endif
 
     AtomicString family = creationParams.family();
     // If we're creating a fallback font (e.g. "-webkit-monospace"), convert the name into
     // the fallback name (like "monospace") that fontconfig understands.
     if (!family.length() || family.startsWith("-webkit-")) {
         name = getFallbackFontFamily(fontDescription).string().utf8();
     } else {
         // convert the name to utf8
@@ skipping 34 matching lines @@
         fontSize,
         (fontDescription.weight() >= FontWeight600 && !tf->isBold()) || fontDescription.isSyntheticBold(),
         (fontDescription.style() && !tf->isItalic()) || fontDescription.isSyntheticItalic(),
         fontDescription.orientation(),
         fontDescription.useSubpixelPositioning());
     return result;
 }
 #endif // !OS(WIN)
 
 } // namespace blink