Remove unused string interpolations.

runtime/lib/growable_array.dart

 // Copyright (c) 2012, 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 _GrowableList<T> implements List<T> {
 
   void insert(int index, T element) {
     if ((index < 0) || (index > length)) {
       throw new RangeError.range(index, 0, length);
     }
@@ skipping 244 matching lines @@
       if (length != initialLength) throw new ConcurrentModificationError(this);
     }
   }
 
   String join([String separator = ""]) {
     if (isEmpty) return "";
     if (this.length == 1) return "${this[0]}";
     StringBuffer buffer = new StringBuffer();
     if (separator.isEmpty) {
       for (int i = 0; i < this.length; i++) {
-        buffer.write("${this[i]}");
+        buffer.write(this[i]);
       }
     } else {
-      buffer.write("${this[0]}");
+      buffer.write(this[0]);
       for (int i = 1; i < this.length; i++) {
         buffer.write(separator);
-        buffer.write("${this[i]}");
+        buffer.write(this[i]);
       }
     }
     return buffer.toString();
   }
 
   Iterable map(f(T element)) {
     return IterableMixinWorkaround.mapList(this, f);
   }
 
   T reduce(T combine(T value, T element)) {
@@ skipping 95 matching lines @@
   }
 
   Set<T> toSet() {
     return new Set<T>.from(this);
   }
 
   Map<int, T> asMap() {
     return new IterableMixinWorkaround<T>().asMapList(this);
   }
 }