Split HForeign into HForeignCode and abstract base class.

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 0bd8d1b953f50022f35771a5b3cce7c89cfacca9..09f4e03d65d39364d49e03ae00a423e71983fe64 100644
--- a/pkg/compiler/lib/src/native/ssa.dart
+++ b/pkg/compiler/lib/src/native/ssa.dart
@@ -85,7 +85,7 @@ void handleSsaNative(SsaBuilder builder, Expression nativeBody) {
     }
 
     builder.push(
-        new HForeign(
+        new HForeignCode(
             // TODO(sra): This could be cached.  The number of templates should
             // be proportional to the number of native methods, which is bounded
             // by the dart: libraries.
@@ -100,7 +100,7 @@ void handleSsaNative(SsaBuilder builder, Expression nativeBody) {
           'functions with zero parameters.');
     }
     LiteralString jsCode = nativeBody.asLiteralString();
-    builder.push(new HForeign.statement(
+    builder.push(new HForeignCode.statement(
         js.js.statementTemplateYielding(
             new js.LiteralStatement(jsCode.dartString.slowToString())),
         <HInstruction>[],