Decouple SSA builder from codegen-work-item

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

Index: pkg/compiler/lib/src/native/ssa.dart
diff --git a/pkg/compiler/lib/src/native/ssa.dart b/pkg/compiler/lib/src/native/ssa.dart
index e75c5290298e2ff8ca853da085b8277fd0b96e2c..1dfa53616256d96f4127c221e2fb30190e2455ba 100644
--- a/pkg/compiler/lib/src/native/ssa.dart
+++ b/pkg/compiler/lib/src/native/ssa.dart
@@ -8,7 +8,7 @@ final RegExp nativeRedirectionRegExp = new RegExp(r'^[a-zA-Z][a-zA-Z_$0-9]*$');
 
 void handleSsaNative(SsaBuilder builder, Expression nativeBody) {
   Compiler compiler = builder.compiler;
-  FunctionElement element = builder.work.element;
+  FunctionElement element = builder.target;
   NativeEmitter nativeEmitter = builder.nativeEmitter;
   JavaScriptBackend backend = builder.backend;
   DiagnosticReporter reporter = compiler.reporter;