Support for interpolated declarations in the js parser.

pkg/compiler/lib/src/js/template.dart

Index: pkg/compiler/lib/src/js/template.dart
diff --git a/pkg/compiler/lib/src/js/template.dart b/pkg/compiler/lib/src/js/template.dart
index 7740431fc05ed717483c4adbbc7e189beac6657e..eb4089ad807090f3b6270d5192658c0e6933e8ad 100644
--- a/pkg/compiler/lib/src/js/template.dart
+++ b/pkg/compiler/lib/src/js/template.dart
@@ -185,6 +185,11 @@ class InstantiatorGeneratorVisitor implements NodeVisitor<Instantiator> {
     return new VariableUse(value);
   }
 
+  static Expression convertStringToVariableDeclaration(String value) {
+    assert(identiferRE.hasMatch(value));
+    return new VariableDeclaration(value);
+  }
+
   Instantiator visitInterpolatedExpression(InterpolatedExpression node) {
     var nameOrPosition = node.nameOrPosition;
     return (arguments) {
@@ -195,6 +200,16 @@ class InstantiatorGeneratorVisitor implements NodeVisitor<Instantiator> {
     };
   }
 
+  Instantiator visitInterpolatedDeclaration(InterpolatedDeclaration node) {
+    var nameOrPosition = node.nameOrPosition;
+    return (arguments) {
+      var value = arguments[nameOrPosition];
+      if (value is Declaration) return value;
+      if (value is String) return convertStringToVariableDeclaration(value);
+      error('Interpolated value #$nameOrPosition is not a declaration: $value');
+    };
+  }
+
   Instantiator visitSplayableExpression(Node node) {
     if (node is InterpolatedExpression) {
       var nameOrPosition = node.nameOrPosition;