Rewrite code to avoid dead code hints during build.

pkg/compiler/lib/src/cps_ir/cps_ir_builder_task.dart

 // Copyright (c) 2013, 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.
 
 library dart2js.ir_builder_task;
 
 import '../closure.dart' as closurelib;
 import '../closure.dart' hide ClosureScope;
 import '../constants/expressions.dart';
 import '../dart_types.dart';
@@ skipping 3167 matching lines @@
 
       case 'JS_CURRENT_ISOLATE_CONTEXT':
         validateArgumentCount(exactly: 0);
 
         if (!compiler.hasIsolateSupport) {
           // If the isolate library is not used, we just generate code
           // to fetch the current isolate.
           String name = backend.namer.currentIsolate;
           return irBuilder.buildForeignCode(js.js.parseForeignJS(name),
               const <ir.Primitive>[], NativeBehavior.PURE);
-        } else {
-          return buildIsolateHelperInvocation('_currentIsolate',
-              CallStructure.NO_ARGS);
         }
-        break;
+        return buildIsolateHelperInvocation('_currentIsolate',
+            CallStructure.NO_ARGS);
 
       case 'JS_CALL_IN_ISOLATE':
         validateArgumentCount(exactly: 2);
 
         if (!compiler.hasIsolateSupport) {
           ir.Primitive closure = visit(argumentNodes.tail.head);
           return irBuilder.buildCallInvocation(closure, CallStructure.NO_ARGS,
               const <ir.Primitive>[]);
-        } else {
-          return buildIsolateHelperInvocation('_callInIsolate',
-              CallStructure.TWO_ARGS);
         }
-        break;
+        return buildIsolateHelperInvocation('_callInIsolate',
+            CallStructure.TWO_ARGS);
 
       default:
         giveup(node, 'unplemented native construct: ${function.name}');
         break;
     }
   }
 
   @override
   ir.Primitive handleStaticFunctionInvoke(ast.Send node,
                                           MethodElement function,
@@ skipping 61 matching lines @@
   }
 
   processSetStatic(ir.SetStatic node) {
     node.body = replacementFor(node.body);
   }
 
   processContinuation(ir.Continuation node) {
     node.body = replacementFor(node.body);
   }
 }