Provide user friendly messages for OTS parsing of fonts

Source/core/fetch/FontResource.h

Index: Source/core/fetch/FontResource.h
diff --git a/Source/core/fetch/FontResource.h b/Source/core/fetch/FontResource.h
index 33b7f0cdbb4e781cfaa663d76ccd32b4b42654e0..c759e4bdc6960ae1713c37fe64879e0bc0b5673a 100644
--- a/Source/core/fetch/FontResource.h
+++ b/Source/core/fetch/FontResource.h
@@ -60,6 +60,7 @@ public:
 
     void setCORSFailed() { 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);
@@ -74,6 +75,7 @@ private:
     enum State { Unloaded, LoadScheduled, LoadInitiated };
 
     OwnPtr<FontCustomPlatformData> m_fontData;
+    String m_otsParsingMessage;
     State m_state;
     bool m_exceedsFontLoadWaitLimit;
     bool m_corsFailed;