Support transformers that depend on other transformers.

sdk/lib/_internal/pub/lib/src/utils.dart

Index: sdk/lib/_internal/pub/lib/src/utils.dart
diff --git a/sdk/lib/_internal/pub/lib/src/utils.dart b/sdk/lib/_internal/pub/lib/src/utils.dart
index 44f530a2778878fab52f6f1d10328d9496fdcc59..a53acb0ca6923c2fc028707c7d235ae6e41c037f 100644
--- a/sdk/lib/_internal/pub/lib/src/utils.dart
+++ b/sdk/lib/_internal/pub/lib/src/utils.dart
@@ -126,6 +126,16 @@ Set setMinus(Iterable minuend, Iterable subtrahend) {
   return minuendSet;
 }
 
+/// Creates a map from [iter], using the return values of [keyFn] as the keys
+/// and the return values of [valueFn] as the values.
+Map listToMap(Iterable iter, keyFn(element), valueFn(element)) {
+  var map = new Map();
+  for (var element in iter) {
+    map[keyFn(element)] = valueFn(element);
+  }
+  return map;
+}
+
 /// Replace each instance of [matcher] in [source] with the return value of
 /// [fn].
 String replace(String source, Pattern matcher, String fn(Match)) {