Make RegExp's constructor non-const.

sdk/lib/_internal/compiler/implementation/js/printer.dart

Index: sdk/lib/_internal/compiler/implementation/js/printer.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js/printer.dart b/sdk/lib/_internal/compiler/implementation/js/printer.dart
index 5bdbfd98b0c2ca90f35c197b7fbd5bee717579f5..e29f7bb489290ded16df154daa433aab8f2e74b2 100644
--- a/sdk/lib/_internal/compiler/implementation/js/printer.dart
+++ b/sdk/lib/_internal/compiler/implementation/js/printer.dart
@@ -15,6 +15,7 @@ class Printer implements NodeVisitor {
   final Namer namer;
   bool pendingSemicolon = false;
   bool pendingSpace = false;
+  static final identifierRegexp = new RegExp(r'^[a-zA-Z_0-9$]');
 
   Printer(leg.Compiler compiler, { allowVariableMinification: true })
       : shouldCompressOutput = compiler.enableMinification,
@@ -46,7 +47,6 @@ class Printer implements NodeVisitor {
 
   void out(String str) {
     if (str != "") {
-      const identifierRegexp = const RegExp(r'^[a-zA-Z_0-9$]');
       if (pendingSemicolon && (!shouldCompressOutput || str != "}")) {
         outBuffer.add(";");
       }
@@ -1067,7 +1067,7 @@ class MinifyRenamer implements Namer {
       codes.add(charCodes.$0 + digit);
       newName = new String.fromCharCodes(codes);
     }
-    assert(const RegExp(r'[a-zA-Z][a-zA-Z0-9]*').hasMatch(newName));
+    assert(new RegExp(r'[a-zA-Z][a-zA-Z0-9]*').hasMatch(newName));
     maps.last[oldName] = newName;
     return newName;
   }