Lower map literals to constructor or function calls in builder

pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart

Index: pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
index b846c878c13e974f1ace9bec719c3024621652a2..67d892bc8d0c5f9e4d04c72308508bd222c4362f 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
@@ -543,17 +543,6 @@ class Builder implements cps_ir.Visitor/*<NodeCallback|Node>*/ {
             translateArguments(node.values));
   }
 
-  Expression visitLiteralMap(cps_ir.LiteralMap node) {
-    return new LiteralMap(
-        node.dartType,
-        new List<LiteralMapEntry>.generate(node.entries.length, (int index) {
-          return new LiteralMapEntry(
-              getVariableUse(node.entries[index].key),
-              getVariableUse(node.entries[index].value));
-        })
-    );
-  }
-
   Expression visitReifyRuntimeType(cps_ir.ReifyRuntimeType node) {
     return new ReifyRuntimeType(
         getVariableUse(node.value), node.sourceInformation);