Make 'where' lazy.

sdk/lib/_internal/compiler/implementation/compile_time_constants.dart

Index: sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart b/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
index 7864e07c26e177f47dc844dc27fa97ef74f08843..1bf46d93812965cfaec283b945b4c6a6c0c185dc 100644
--- a/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
+++ b/sdk/lib/_internal/compiler/implementation/compile_time_constants.dart
@@ -184,11 +184,11 @@ class ConstantHandler extends CompilerTask {
   }
 
   /**
-   * Returns a [List] of static non final fields that need to be initialized.
-   * The list must be evaluated in order since the fields might depend on each
-   * other.
+   * Returns an [Iterable] of static non final fields that need to be
+   * initialized. The fields list must be evaluated in order since they might
+   * depend on each other.
    */
-  List<VariableElement> getStaticNonFinalFieldsForEmission() {
+  Iterable<VariableElement> getStaticNonFinalFieldsForEmission() {
     return initialVariableValues.keys.where((element) {
       return element.kind == ElementKind.FIELD
           && !element.isInstanceMember()
@@ -197,11 +197,11 @@ class ConstantHandler extends CompilerTask {
   }
 
   /**
-   * Returns a [List] of static const fields that need to be initialized. The
-   * list must be evaluated in order since the fields might depend on each
+   * Returns an [Iterable] of static const fields that need to be initialized.
+   * The fields must be evaluated in order since they might depend on each
    * other.
    */
-  List<VariableElement> getStaticFinalFieldsForEmission() {
+  Iterable<VariableElement> getStaticFinalFieldsForEmission() {
     return initialVariableValues.keys.where((element) {
       return element.kind == ElementKind.FIELD
           && !element.isInstanceMember()