Remove BackendClasses and JavaScriptBackendClasses.

pkg/compiler/lib/src/ssa/interceptor_simplifier.dart

Index: pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
diff --git a/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart b/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
index 08c0d9a7f479eb9cb16f447641afca437c0329e0..dad06b9456d53d0db4f49573f5f1353a455116e8 100644
--- a/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
+++ b/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
@@ -3,7 +3,6 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import '../common_elements.dart' show CommonElements;
-import '../common/backend_api.dart' show BackendClasses;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
 import '../elements/entities.dart';
@@ -46,8 +45,6 @@ class SsaSimplifyInterceptors extends HBaseVisitor
   SsaSimplifyInterceptors(this.closedWorld, this._commonElements,
       this.interceptorData, this.enclosingClass);
 
-  BackendClasses get backendClasses => closedWorld.backendClasses;
-
   ConstantSystem get constantSystem => closedWorld.constantSystem;
 
   void visitGraph(HGraph graph) {
@@ -101,7 +98,7 @@ class SsaSimplifyInterceptors extends HBaseVisitor
       return false;
     }
     if (receiver.canBeNull() &&
-        interceptedClasses.contains(backendClasses.nullClass)) {
+        interceptedClasses.contains(_commonElements.jsNullClass)) {
       // Need the JSNull interceptor.
       return false;
     }
@@ -142,25 +139,25 @@ class SsaSimplifyInterceptors extends HBaseVisitor
       TypeMask type, Set<ClassEntity> interceptedClasses) {
     if (type.isNullable) {
       if (type.isNull) {
-        return backendClasses.nullClass;
+        return _commonElements.jsNullClass;
       }
     } else if (type.containsOnlyInt(closedWorld)) {
-      return backendClasses.intClass;
+      return _commonElements.jsIntClass;
     } else if (type.containsOnlyDouble(closedWorld)) {
-      return backendClasses.doubleClass;
+      return _commonElements.jsDoubleClass;
     } else if (type.containsOnlyBool(closedWorld)) {
-      return backendClasses.boolClass;
+      return _commonElements.jsBoolClass;
     } else if (type.containsOnlyString(closedWorld)) {
-      return backendClasses.stringClass;
-    } else if (type.satisfies(backendClasses.listClass, closedWorld)) {
-      return backendClasses.listClass;
+      return _commonElements.jsStringClass;
+    } else if (type.satisfies(_commonElements.jsArrayClass, closedWorld)) {
+      return _commonElements.jsArrayClass;
     } else if (type.containsOnlyNum(closedWorld) &&
-        !interceptedClasses.contains(backendClasses.intClass) &&
-        !interceptedClasses.contains(backendClasses.doubleClass)) {
+        !interceptedClasses.contains(_commonElements.jsIntClass) &&
+        !interceptedClasses.contains(_commonElements.jsDoubleClass)) {
       // If the method being intercepted is not defined in [int] or [double] we
       // can safely use the number interceptor.  This is because none of the
       // [int] or [double] methods are called from a method defined on [num].
-      return backendClasses.numClass;
+      return _commonElements.jsNumberClass;
     } else {
       // Try to find constant interceptor for a native class.  If the receiver
       // is constrained to a leaf native class, we can use the class's
@@ -174,7 +171,7 @@ class SsaSimplifyInterceptors extends HBaseVisitor
       // code is completely insensitive to the specific instance subclasses, we
       // can use the non-leaf class directly.
       ClassEntity element = type.singleClass(closedWorld);
-      if (element != null && backendClasses.isNativeClass(element)) {
+      if (element != null && closedWorld.nativeData.isNativeClass(element)) {
         return element;
       }
     }
@@ -229,25 +226,25 @@ class SsaSimplifyInterceptors extends HBaseVisitor
 
       // If we found that we need number, we must still go through all
       // uses to check if they require int, or double.
-      if (interceptedClasses.contains(backendClasses.numClass) &&
-          !(interceptedClasses.contains(backendClasses.doubleClass) ||
-              interceptedClasses.contains(backendClasses.intClass))) {
+      if (interceptedClasses.contains(_commonElements.jsNumberClass) &&
+          !(interceptedClasses.contains(_commonElements.jsDoubleClass) ||
+              interceptedClasses.contains(_commonElements.jsIntClass))) {
         Set<ClassEntity> required;
         for (HInstruction user in node.usedBy) {
           if (user is! HInvoke) continue;
           Set<ClassEntity> intercepted =
               interceptorData.getInterceptedClassesOn(user.selector.name);
-          if (intercepted.contains(backendClasses.intClass)) {
+          if (intercepted.contains(_commonElements.jsIntClass)) {
             // TODO(johnniwinther): Use type argument when all uses of
             // intercepted classes expect entities instead of elements.
             required ??= new Set/*<ClassEntity>*/();
-            required.add(backendClasses.intClass);
+            required.add(_commonElements.jsIntClass);
           }
-          if (intercepted.contains(backendClasses.doubleClass)) {
+          if (intercepted.contains(_commonElements.jsDoubleClass)) {
             // TODO(johnniwinther): Use type argument when all uses of
             // intercepted classes expect entities instead of elements.
             required ??= new Set/*<ClassEntity>*/();
-            required.add(backendClasses.doubleClass);
+            required.add(_commonElements.jsDoubleClass);
           }
         }
         // Don't modify the result of [interceptorData.getInterceptedClassesOn].
@@ -315,7 +312,7 @@ class SsaSimplifyInterceptors extends HBaseVisitor
     // constant interceptor `C`.  Then we can use `(receiver && C)` for the
     // interceptor.
     if (receiver.canBeNull()) {
-      if (!interceptedClasses.contains(backendClasses.nullClass)) {
+      if (!interceptedClasses.contains(_commonElements.jsNullClass)) {
         // Can use `(receiver && C)` only if receiver is either null or truthy.
         if (!(receiver.canBePrimitiveNumber(closedWorld) ||
             receiver.canBePrimitiveBoolean(closedWorld) ||