Add FrontendStrategy.commonElements and remove Backend.commonElements

pkg/compiler/lib/src/inferrer/closure_tracer.dart

Index: pkg/compiler/lib/src/inferrer/closure_tracer.dart
diff --git a/pkg/compiler/lib/src/inferrer/closure_tracer.dart b/pkg/compiler/lib/src/inferrer/closure_tracer.dart
index 1f9bb63d05601202d5fdfbc77ec0f33564e01161..88fd7fcb9986c1e5539532ddf3f5e2284acee8a4 100644
--- a/pkg/compiler/lib/src/inferrer/closure_tracer.dart
+++ b/pkg/compiler/lib/src/inferrer/closure_tracer.dart
@@ -77,7 +77,7 @@ class ClosureTracerVisitor extends TracerVisitor {
   visitStaticCallSiteTypeInformation(StaticCallSiteTypeInformation info) {
     super.visitStaticCallSiteTypeInformation(info);
     Element called = info.calledElement;
-    if (compiler.backend.isForeign(called)) {
+    if (compiler.backend.isForeign(compiler.commonElements, called)) {
       String name = called.name;
       if (name == JavaScriptBackend.JS || name == 'DART_CLOSURE_TO_JS') {
         bailout('Used in JS ${info.call}');