Provide user friendly messages for OTS parsing of fonts

Source/core/fetch/FontResource.h

 /*
  * Copyright (C) 2007, 2008 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 43 matching lines @@
     void beginLoadIfNeeded(ResourceFetcher* dl);
     virtual bool stillNeedsLoad() const override { return m_state != LoadInitiated; }
     bool exceedsFontLoadWaitLimit() const { return m_exceedsFontLoadWaitLimit; }
 
     bool loadScheduled() const { return m_state != Unloaded; }
     void didScheduleLoad();
     void didUnscheduleLoad();
 
     void setCORSFailed() override { m_corsFailed = true; }
     bool isCORSFailed() const { return m_corsFailed; }
+    String otsParsingMessage() const { return m_otsParsingMessage; }
 
     bool ensureCustomFontData();
     FontPlatformData platformDataFromCustomData(float size, bool bold, bool italic, FontOrientation = FontOrientation::Horizontal);
 
 protected:
     virtual bool isSafeToUnlock() const override;
 
 private:
     class FontResourceFactory : public ResourceFactory {
     public:
         FontResourceFactory()
             : ResourceFactory(Resource::Font) { }
 
         Resource* create(const ResourceRequest& request, const String& charset) const override
         {
             return new FontResource(request);
         }
     };
     FontResource(const ResourceRequest&);
 
     virtual void checkNotify() override;
     void fontLoadWaitLimitCallback(Timer<FontResource>*);
 
     enum State { Unloaded, LoadScheduled, LoadInitiated };
 
     OwnPtr<FontCustomPlatformData> m_fontData;
+    String m_otsParsingMessage;
     State m_state;
     bool m_exceedsFontLoadWaitLimit;
     bool m_corsFailed;
     Timer<FontResource> m_fontLoadWaitLimitTimer;
 
     friend class MemoryCache;
 };
 
 DEFINE_RESOURCE_TYPE_CASTS(Font);
 
 class FontResourceClient : public ResourceClient {
 public:
     virtual ~FontResourceClient() { }
     static ResourceClientType expectedType() { return FontType; }
     virtual ResourceClientType resourceClientType() const override final { return expectedType(); }
     virtual void fontLoaded(FontResource*) { }
     virtual void didStartFontLoad(FontResource*) { }
     virtual void fontLoadWaitLimitExceeded(FontResource*) { }
 };
 
 }
 
 #endif