Extract InterceptorData from JavaScriptBackend.

pkg/compiler/lib/src/js_emitter/native_emitter.dart

 // Copyright (c) 2012, 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.js_emitter.native_emitter;
 
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../elements/types.dart' show DartType, FunctionType;
 import '../elements/entities.dart';
@@ skipping 328 matching lines @@
         receiver = js('this');
       }
     }
     statements
         .add(js.statement('return #.#(#)', [receiver, target, arguments]));
 
     return statements;
   }
 
   bool isSupertypeOfNativeClass(ClassEntity element) {
-    if (backend.classesMixedIntoInterceptedClasses.contains(element)) {
+    if (backend.interceptorData.classesMixedIntoInterceptedClasses
+        .contains(element)) {
       return true;
     }
 
     return subtypes[element] != null;
   }
 
   bool requiresNativeIsCheck(ClassEntity element) {
     // TODO(sra): Remove this function.  It determines if a native type may
     // satisfy a check against [element], in which case an interceptor must be
     // used.  We should also use an interceptor if the check can't be satisfied
     // by a native class in case we get a native instance that tries to spoof
     // the type info.  i.e the criteria for whether or not to use an interceptor
     // is whether the receiver can be native, not the type of the test.
     ClassEntity cls = element;
-    if (backend.isNativeOrExtendsNative(cls)) return true;
+    if (backend.nativeData.isNativeOrExtendsNative(cls)) return true;
     return isSupertypeOfNativeClass(element);
   }
 }