Rename ClosureVariable, use separate IR forms for declaration and assignment.

pkg/analyzer2dart/test/sexpr_data.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Test data for sexpr_test.
 library test.sexpr.data;
 
 import 'test_helper.dart';
 
 class TestSpec extends TestSpecBase {
@@ skipping 1354 matching lines @@
 main(x,foo) {
   print(x);
   getFoo() => foo;
   print(getFoo());
 }
 ''', '''
 (FunctionDefinition main (x foo) return
   (LetCont ((k0 (v0)
       (LetPrim (v1 (CreateFunction
           (FunctionDefinition getFoo () return
-            (LetPrim (v2 (GetClosureVariable foo))
+            (LetPrim (v2 (GetMutableVariable foo))
               (InvokeContinuation return (v2))))))
         (LetCont ((k1 (v3)
             (LetCont ((k2 (v4)
                 (LetPrim (v5 (Constant (Null)))
                   (InvokeContinuation return (v5)))))
               (InvokeStatic print (v3) k2))))
           (InvokeMethod v1 call () k1)))))
     (InvokeStatic print (x) k0)))
 ''', skipInAnalyzerFrontend: true)
   ]),
@@ skipping 14 matching lines @@
       (InvokeContinuation return (v0))))
     (InvokeConstructor C () k0)))
 ''',
 'C.': '''
 (FunctionDefinition  () return
   (LetPrim (v0 (Constant (Null)))
     (InvokeContinuation return (v0))))
 '''}),
   ]),
 ];