Fix some warnings.

lib/dom/templates/html/impl/impl_DocumentFragment.darttemplate

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class FilteredElementList implements ElementList {
   final Node _node;
   final NodeList _childNodes;
 
   FilteredElementList(Node node): _childNodes = node.nodes, _node = node;
 
@@ skipping 46 matching lines @@
   }
 
   void sort(int compare(Element a, Element b)) {
     throw const UnsupportedOperationException('TODO(jacobr): should we impl?');
   }
 
   void copyFrom(List<Object> src, int srcStart, int dstStart, int count) {
     throw const NotImplementedException();
   }
 
-  void setRange(int start, int length, List from, [int startFrom = 0]) {
+  void setRange(int start, int rangeLength, List from, [int startFrom = 0]) {
     throw const NotImplementedException();
   }
 
-  void removeRange(int start, int length) {
-    _filtered.getRange(start, length).forEach((el) => el.remove());
+  void removeRange(int start, int rangeLength) {
+    _filtered.getRange(start, rangeLength).forEach((el) => el.remove());
   }
 
-  void insertRange(int start, int length, [initialValue = null]) {
+  void insertRange(int start, int rangeLength, [initialValue = null]) {
     throw const NotImplementedException();
   }
 
   void clear() {
     // Currently, ElementList#clear clears even non-element nodes, so we follow
     // that behavior.
     _childNodes.clear();
   }
 
   Element removeLast() {
-    final last = this.last();
-    if (last != null) {
-      last.remove();
+    final result = this.last();
+    if (result != null) {
+      result.remove();
     }
-    return last;
+    return result;
   }
 
   Collection map(f(Element element)) => _filtered.map(f);
   Collection<Element> filter(bool f(Element element)) => _filtered.filter(f);
   bool every(bool f(Element element)) => _filtered.every(f);
   bool some(bool f(Element element)) => _filtered.some(f);
   bool isEmpty() => _filtered.isEmpty();
   int get length() => _filtered.length;
   Element operator [](int index) => _filtered[index];
   Iterator<Element> iterator() => _filtered.iterator();
-  List<Element> getRange(int start, int length) =>
-    _filtered.getRange(start, length);
+  List<Element> getRange(int start, int rangeLength) =>
+    _filtered.getRange(start, rangeLength);
   int indexOf(Element element, [int start = 0]) =>
     _filtered.indexOf(element, start);
 
   int lastIndexOf(Element element, [int start = null]) {
     if (start === null) start = length - 1;
     return _filtered.lastIndexOf(element, start);
   }
 
   Element last() => _filtered.last();
 }
@@ skipping 222 matching lines @@
       "WebKit drop zone can't be set for document fragments.");
   }
 
   void set webkitRegionOverflow(String value) {
     throw new UnsupportedOperationException(
       "WebKit region overflow can't be set for document fragments.");
   }
 
 $!MEMBERS
 }