Extract InterceptorData from JavaScriptBackend.

pkg/compiler/lib/src/js_emitter/program_builder/collector.dart

Index: pkg/compiler/lib/src/js_emitter/program_builder/collector.dart
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder/collector.dart b/pkg/compiler/lib/src/js_emitter/program_builder/collector.dart
index cbcec387c541719c58435d470f53c8469701f835..48b333c00e310ebd50876189f7233c1df91ec78f 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder/collector.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder/collector.dart
@@ -78,7 +78,7 @@ class Collector {
     // Go over specialized interceptors and then constants to know which
     // interceptors are needed.
     Set<ClassElement> needed = new Set<ClassElement>();
-    backend.specializedGetInterceptors
+    backend.interceptorData.specializedGetInterceptors
         .forEach((_, Iterable<ClassElement> elements) {
       needed.addAll(elements);
     });
@@ -87,7 +87,8 @@ class Collector {
     needed.addAll(computeInterceptorsReferencedFromConstants());
 
     // Add unneeded interceptors to the [unneededClasses] set.
-    for (ClassElement interceptor in backend.interceptedClasses) {
+    for (ClassElement interceptor
+        in backend.interceptorData.interceptedClasses) {
       if (!needed.contains(interceptor) &&
           interceptor != commonElements.objectClass) {
         unneededClasses.add(interceptor);
@@ -243,7 +244,7 @@ class Collector {
     List<ClassElement> sortedClasses = Elements.sortedByPosition(neededClasses);
 
     for (ClassElement element in sortedClasses) {
-      if (backend.isNativeOrExtendsNative(element) &&
+      if (backend.nativeData.isNativeOrExtendsNative(element) &&
           !classesOnlyNeededForRti.contains(element)) {
         // For now, native classes and related classes cannot be deferred.
         nativeClassesAndSubclasses.add(element);