Adapt private variables with trailing underscores.

sdk/lib/_collection_dev/sort.dart

Index: sdk/lib/_collection_dev/sort.dart
diff --git a/sdk/lib/_collection_dev/sort.dart b/sdk/lib/_collection_dev/sort.dart
index 73276b231ce84ec1c1bf9455274683a49eca1b5e..9bc7c9abfad3b3895135aa9e12fbbe9511e7d6c0 100644
--- a/sdk/lib/_collection_dev/sort.dart
+++ b/sdk/lib/_collection_dev/sort.dart
@@ -54,13 +54,13 @@ class Sort {
    */
   static void _doSort(List a, int left, int right, int compare(a, b)) {
     if ((right - left) <= _INSERTION_SORT_THRESHOLD) {
-      insertionSort_(a, left, right, compare);
+      _insertionSort(a, left, right, compare);
     } else {
       _dualPivotQuicksort(a, left, right, compare);
     }
   }
 
-  static void insertionSort_(List a, int left, int right, int compare(a, b)) {
+  static void _insertionSort(List a, int left, int right, int compare(a, b)) {
     for (int i = left + 1; i <= right; i++) {
       var el = a[i];
       int j = i;