Improve core/css exception messages.

Source/core/css/CSSStyleSheet.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 242 matching lines @@
         nonCharsetRules->rules().append(rule);
     }
     return nonCharsetRules.release();
 }
 
 unsigned CSSStyleSheet::insertRule(const String& ruleString, unsigned index, ExceptionState& exceptionState)
 {
     ASSERT(m_childRuleCSSOMWrappers.isEmpty() || m_childRuleCSSOMWrappers.size() == m_contents->ruleCount());
 
     if (index > length()) {
-        exceptionState.throwUninformativeAndGenericDOMException(IndexSizeError);
+        exceptionState.throwDOMException(IndexSizeError, "The index provided (" + String::number(index) + ") is larger than the maximum index (" + String::number(length()) + ").");
         return 0;
     }
     BisonCSSParser p(m_contents->parserContext(), UseCounter::getFrom(this));
     RefPtr<StyleRuleBase> rule = p.parseRule(m_contents.get(), ruleString);
 
     if (!rule) {
-        exceptionState.throwUninformativeAndGenericDOMException(SyntaxError);
+        exceptionState.throwDOMException(SyntaxError, "Failed to parse the rule '" + ruleString + "'.");
         return 0;
     }
     RuleMutationScope mutationScope(this);
 
     bool success = m_contents->wrapperInsertRule(rule, index);
     if (!success) {
-        exceptionState.throwUninformativeAndGenericDOMException(HierarchyRequestError);
+        exceptionState.throwDOMException(HierarchyRequestError, "Failed to insert the rule.");
         return 0;
     }
     if (!m_childRuleCSSOMWrappers.isEmpty())
         m_childRuleCSSOMWrappers.insert(index, RefPtr<CSSRule>());
 
     return index;
 }
 
 unsigned CSSStyleSheet::insertRule(const String& rule, ExceptionState& exceptionState)
 {
     UseCounter::countDeprecation(activeExecutionContext(), UseCounter::CSSStyleSheetInsertRuleOptionalArg);
     return insertRule(rule, 0, exceptionState);
 }
 
 void CSSStyleSheet::deleteRule(unsigned index, ExceptionState& exceptionState)
 {
     ASSERT(m_childRuleCSSOMWrappers.isEmpty() || m_childRuleCSSOMWrappers.size() == m_contents->ruleCount());
 
     if (index >= length()) {
-        exceptionState.throwUninformativeAndGenericDOMException(IndexSizeError);
+        exceptionState.throwDOMException(IndexSizeError, "The index provided (" + String::number(index) + ") is larger than the maximum index (" + String::number(length() - 1) + ").");
         return;
     }
     RuleMutationScope mutationScope(this);
 
     m_contents->wrapperDeleteRule(index);
 
     if (!m_childRuleCSSOMWrappers.isEmpty()) {
         if (m_childRuleCSSOMWrappers[index])
             m_childRuleCSSOMWrappers[index]->setParentStyleSheet(0);
         m_childRuleCSSOMWrappers.remove(index);
@@ skipping 67 matching lines @@
         root = root->parentStyleSheet();
     return root->ownerNode() ? &root->ownerNode()->document() : 0;
 }
 
 void CSSStyleSheet::clearChildRuleCSSOMWrappers()
 {
     m_childRuleCSSOMWrappers.clear();
 }
 
 }