Revert "special-case ListMixin.setRange from same list"

sdk/lib/collection/list.dart

Index: sdk/lib/collection/list.dart
diff --git a/sdk/lib/collection/list.dart b/sdk/lib/collection/list.dart
index 92b1110b192500795207b14ccb9491d57c7b696c..7f476dc9aa2023de4b9aceb1a924dc3584eee15c 100644
--- a/sdk/lib/collection/list.dart
+++ b/sdk/lib/collection/list.dart
@@ -256,27 +256,14 @@ abstract class ListMixin<E> implements List<E> {
   bool remove(Object element) {
     for (int i = 0; i < this.length; i++) {
       if (this[i] == element) {
-        this._closeGap(i, i + 1);
+        this.setRange(i, this.length - 1, this, i + 1);
+        this.length -= 1;
         return true;
       }
     }
     return false;
   }
 
-  /// Removes elements from the list starting at [start] up to but not including
-  /// [end].  Arguments are pre-validated.
-  void _closeGap(int start, int end) {
-    int length = this.length;
-    assert(0 <= start);
-    assert(start < end);
-    assert(end <= length);
-    int size = end - start;
-    for (int i = end; i < length; i++) {
-      this[i - size] = this[i];
-    }
-    this.length = length - size;
-  }
-
   void removeWhere(bool test(E element)) {
     _filter(test, false);
   }
@@ -363,9 +350,9 @@ abstract class ListMixin<E> implements List<E> {
 
   void removeRange(int start, int end) {
     RangeError.checkValidRange(start, end, this.length);
-    if (end > start) {
-      _closeGap(start, end);
-    }
+    int length = end - start;
+    setRange(start, this.length - length, this, end);
+    this.length -= length;
   }
 
   void fillRange(int start, int end, [E fill]) {
@@ -414,10 +401,13 @@ abstract class ListMixin<E> implements List<E> {
     int removeLength = end - start;
     int insertLength = newContents.length;
     if (removeLength >= insertLength) {
+      int delta = removeLength - insertLength;
       int insertEnd = start + insertLength;
+      int newLength = this.length - delta;
       this.setRange(start, insertEnd, newContents);
-      if (removeLength > insertLength) {
-        _closeGap(insertEnd, end);
+      if (delta != 0) {
+        this.setRange(insertEnd, newLength, this, end);
+        this.length = newLength;
       }
     } else {
       int delta = insertLength - removeLength;
@@ -480,7 +470,8 @@ abstract class ListMixin<E> implements List<E> {
 
   E removeAt(int index) {
     E result = this[index];
-    _closeGap(index, index + 1);
+    setRange(index, this.length - 1, this, index + 1);
+    length--;
     return result;
   }