Changed UnsupportedOperationException to UnsupportedError

lib/dom_parsing.dart

Index: lib/dom_parsing.dart
diff --git a/lib/dom_parsing.dart b/lib/dom_parsing.dart
index b2a2de1d4ba8b4d4b5ce9f5e43c934bd44411809..83491a928a5cc0a9257ad7ff3aaf9dabcb22edb0 100644
--- a/lib/dom_parsing.dart
+++ b/lib/dom_parsing.dart
@@ -133,7 +133,7 @@ class SourceFileInfo {
   /** Gets the text at the given offsets. */
   String getText(int start, [int end]) {
     if (_decodedChars == null) {
-      throw new UnsupportedOperationException('getText is only supported '
+      throw new UnsupportedError('getText is only supported '
           'if parser.generateSpans is true.');
     }
 
@@ -160,7 +160,7 @@ class SourceFileInfo {
     if (!includeText) return msg;
 
     if (_decodedChars == null) {
-      throw new UnsupportedOperationException('includeText is only supported '
+      throw new UnsupportedError('includeText is only supported '
           'if parser.generateSpans is true.');
     }
 
@@ -212,8 +212,7 @@ class TreeVisitor {
       case Node.DOCUMENT_FRAGMENT_NODE: return visitDocumentFragment(node);
       case Node.DOCUMENT_NODE: return visitDocument(node);
       case Node.DOCUMENT_TYPE_NODE: return visitDocumentType(node);
-      default: throw new UnsupportedOperationException(
-          'DOM node type ${node.nodeType}');
+      default: throw new UnsupportedError('DOM node type ${node.nodeType}');
     }
   }