Add source information to variable declarations in CPS.

pkg/compiler/lib/src/js_backend/codegen/codegen.dart

Index: pkg/compiler/lib/src/js_backend/codegen/codegen.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/codegen.dart b/pkg/compiler/lib/src/js_backend/codegen/codegen.dart
index 4d0f49709bb157cb289afe8722d6d774dbb08d0b..9f1947f79bf6438f397ab8818d69c83f28c5faf8 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/codegen.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/codegen.dart
@@ -184,7 +184,8 @@ class CodeGenerator extends tree_ir.StatementVisitor
     if (jsVariables.length > 0) {
       // Would be nice to avoid inserting at the beginning of list.
       accumulator.insert(0, new js.ExpressionStatement(
-          new js.VariableDeclarationList(jsVariables)));
+          new js.VariableDeclarationList(jsVariables)
+              .withSourceInformation(function.sourceInformation)));
     }
     return new js.Fun(parameters, new js.Block(accumulator));
   }