Add FrontendStrategy.commonElements and remove Backend.commonElements

pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart b/pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart
index d1651f5f5261ffe9db09f465cae566529537d947..66e880b7f27ed60e9b7ca3304352d25d4828404f 100644
--- a/pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/full_emitter/interceptor_emitter.dart
@@ -57,8 +57,8 @@ class InterceptorEmitter extends CodeEmitterHelper {
       Set<ClassEntity> classes =
           backend.oneShotInterceptorData.getSpecializedGetInterceptorsFor(name);
       parts.add(js.statement('#.# = #', [
-        namer
-            .globalObjectForLibrary(backend.commonElements.interceptorsLibrary),
+        namer.globalObjectForLibrary(
+            closedWorld.commonElements.interceptorsLibrary),
         name,
         buildGetInterceptorMethod(name, classes)
       ]));
@@ -74,7 +74,7 @@ class InterceptorEmitter extends CodeEmitterHelper {
 
     InterceptorStubGenerator stubGenerator = new InterceptorStubGenerator(
         compiler.options,
-        compiler.commonElements,
+        closedWorld.commonElements,
         backend.emitter,
         backend.nativeCodegenEnqueuer,
         namer,
@@ -83,7 +83,7 @@ class InterceptorEmitter extends CodeEmitterHelper {
         compiler.codegenWorldBuilder,
         closedWorld);
     String globalObject = namer
-        .globalObjectForLibrary(backend.commonElements.interceptorsLibrary);
+        .globalObjectForLibrary(closedWorld.commonElements.interceptorsLibrary);
     for (jsAst.Name name in names) {
       jsAst.Expression function =
           stubGenerator.generateOneShotInterceptor(name);