Improve core/css exception messages.

Source/core/css/FontFace.cpp

 /*
  * Copyright (C) 2013 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 84 matching lines @@
         return 0;
     RefPtr<MutableStylePropertySet> parsedStyle = MutableStylePropertySet::create();
     BisonCSSParser::parseValue(parsedStyle.get(), propertyID, s, true, HTMLStandardMode, 0);
     return parsedStyle->getPropertyCSSValue(propertyID);
 }
 
 PassRefPtr<FontFace> FontFace::create(const AtomicString& family, const String& source, const Dictionary& descriptors, ExceptionState& exceptionState)
 {
     RefPtr<CSSValue> src = parseCSSValue(source, CSSPropertySrc);
     if (!src || !src->isValueList()) {
-        exceptionState.throwUninformativeAndGenericDOMException(SyntaxError);
+        exceptionState.throwDOMException(SyntaxError, "The source provided ('" + source + "') could not be parsed as a value list.");
         return 0;
     }
 
     RefPtr<FontFace> fontFace = adoptRef<FontFace>(new FontFace(src));
     fontFace->setFamily(family, exceptionState);
     if (exceptionState.hadException())
         return 0;
 
     String value;
     if (descriptors.get("style", value)) {
@@ skipping 123 matching lines @@
 
 void FontFace::setFeatureSettings(const String& s, ExceptionState& exceptionState)
 {
     setPropertyFromString(s, CSSPropertyWebkitFontFeatureSettings, exceptionState);
 }
 
 void FontFace::setPropertyFromString(const String& s, CSSPropertyID propertyID, ExceptionState& exceptionState)
 {
     RefPtr<CSSValue> value = parseCSSValue(s, propertyID);
     if (!value || !setPropertyValue(value, propertyID))
-        exceptionState.throwUninformativeAndGenericDOMException(SyntaxError);
+        exceptionState.throwDOMException(SyntaxError, "Failed to set '" + s + "' as a property value.");
 }
 
 bool FontFace::setPropertyFromStyle(const StylePropertySet* properties, CSSPropertyID propertyID)
 {
     return setPropertyValue(properties->getPropertyCSSValue(propertyID), propertyID);
 }
 
 bool FontFace::setPropertyValue(PassRefPtr<CSSValue> value, CSSPropertyID propertyID)
 {
     switch (propertyID) {
@@ skipping 271 matching lines @@
         unsigned numRanges = rangeList->length();
         for (unsigned i = 0; i < numRanges; i++) {
             CSSUnicodeRangeValue* range = toCSSUnicodeRangeValue(rangeList->itemWithoutBoundsCheck(i));
             cssFontFace->ranges().add(range->from(), range->to());
         }
     }
     return cssFontFace;
 }
 
 } // namespace WebCore