Provide user friendly messages for OTS parsing of fonts

Source/platform/fonts/FontCustomPlatformData.cpp

 /*
  * Copyright (C) 2007 Apple Computer, Inc.
  * Copyright (c) 2007, 2008, 2009, Google Inc. All rights reserved.
  * Copyright (C) 2010 Company 100, Inc.
  *
  * 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
@@ skipping 67 matching lines @@
             RefPtr<SkTypeface> typeface = adoptRef(FontCache::fontCache()->fontManager()->legacyCreateTypeface(name.c_str(), static_cast<SkTypeface::Style>(style)));
             syntheticBold = false;
             syntheticItalic = false;
             return FontPlatformData(typeface.release(), "", size, syntheticBold, syntheticItalic, orientation);
         }
     }
 #endif
     return FontPlatformData(m_typeface.get(), "", size, bold && !m_typeface->isBold(), italic && !m_typeface->isItalic(), orientation);
 }
 
-PassOwnPtr<FontCustomPlatformData> FontCustomPlatformData::create(SharedBuffer* buffer)
+PassOwnPtr<FontCustomPlatformData> FontCustomPlatformData::create(SharedBuffer* buffer, String& otsParseMessage)
 {
     ASSERT_ARG(buffer, buffer);
 
     OpenTypeSanitizer sanitizer(buffer);
     RefPtr<SharedBuffer> transcodeBuffer = sanitizer.sanitize();
-    if (!transcodeBuffer)
+
+    if (!transcodeBuffer) {

[jungshik at Google, 2015/05/15 19:17:20]

I took a look at sanitize() to find that there are two  cases where
|transcodeBuffer == nullptr} but |m_parsingError| is uninitialized. So checking
|!transcodeBuffer| makes sense. 

[h.joshi, 2015/05/18 05:58:28]

Method "setParsingError" was not called at right place. Corrected that in new
patch.

+        otsParseMessage = sanitizer.getErrorString();
         return nullptr; // validation failed.
+    }
     buffer = transcodeBuffer.get();
 
     SkMemoryStream* stream = new SkMemoryStream(buffer->getAsSkData().get());
 #if OS(WIN)
     RefPtr<SkTypeface> typeface = adoptRef(FontCache::fontCache()->fontManager()->createFromStream(stream));
 #else
     RefPtr<SkTypeface> typeface = adoptRef(SkTypeface::CreateFromStream(stream));
 #endif
     if (!typeface)
         return nullptr;
 
     return adoptPtr(new FontCustomPlatformData(typeface.release()));
 }
 
 bool FontCustomPlatformData::supportsFormat(const String& format)
 {
     return equalIgnoringCase(format, "truetype") || equalIgnoringCase(format, "opentype") || OpenTypeSanitizer::supportsFormat(format);
 }
 
 } // namespace blink