Provide user friendly messages for OTS parsing of fonts

Source/platform/fonts/FontCustomPlatformData.cpp

Index: Source/platform/fonts/FontCustomPlatformData.cpp
diff --git a/Source/platform/fonts/FontCustomPlatformData.cpp b/Source/platform/fonts/FontCustomPlatformData.cpp
index 1cae8696dde0622b8f6c7993a978996dd3b131e5..4920ea8c52e7ea4638fdf36ecf823ff5b823e1df 100644
--- a/Source/platform/fonts/FontCustomPlatformData.cpp
+++ b/Source/platform/fonts/FontCustomPlatformData.cpp
@@ -85,14 +85,19 @@ FontPlatformData FontCustomPlatformData::fontPlatformData(float size, bool bold,
     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) {
+        // If error was faced at time of OTS parsing, we need to pass on OTS error to Blink
+        if (sanitizer.isParsingError())
+            otsParseMessage = sanitizer.getErrorString();

[jungshik at Google, 2015/06/01 23:22:19]

If you set |errorString| whenever sanitize() returns empty buffer, you don't
need a separate isParsingError() check  (and m_ParsingError in OTSSanitizer is
NOT necessary, either).  

Alternatively, you can set 'parsingError' to true and set |errorString| 
whenever you return 'empty' buffer, but it seems redundant to do that way. 

Either way, I don't see a reason to use two if-statements here. 

[h.joshi, 2015/06/04 15:19:16]

Done.

         return nullptr; // validation failed.
+    }
     buffer = transcodeBuffer.get();
 
     SkMemoryStream* stream = new SkMemoryStream(buffer->getAsSkData().get());