Use native types for inlined native fields.

sdk/lib/_internal/compiler/implementation/ssa/optimize.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart b/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
index 2937791dc16636b811fdcc4e625bf6f9c5080460..973377c78356f1123fa78383787cc2cc9c5fdb51 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
@@ -690,8 +690,9 @@ class SsaConstantFolder extends HBaseVisitor implements OptimizationPhase {
         field, receiver, isAssignable: isAssignable);
 
     if (field.getEnclosingClass().isNative()) {
-      result.instructionType =
-          new HType.subtype(field.computeType(compiler), compiler);
+      result.instructionType = new HType.fromNativeBehavior(
+          native.NativeBehavior.ofFieldLoad(field, compiler),
+          compiler);
     } else {
       HType type = new HType.inferredTypeForElement(field, compiler);
       if (type.isUnknown()) {