Mark ForeignCode as isSafeForElimination when it has no effects or exceptions.

pkg/compiler/lib/src/cps_ir/type_propagation.dart

Index: pkg/compiler/lib/src/cps_ir/type_propagation.dart
diff --git a/pkg/compiler/lib/src/cps_ir/type_propagation.dart b/pkg/compiler/lib/src/cps_ir/type_propagation.dart
index b36440e9228c887e26776414047c4743c48bd975..1da858fc2335174ca61df1af924a97be16a1c185 100644
--- a/pkg/compiler/lib/src/cps_ir/type_propagation.dart
+++ b/pkg/compiler/lib/src/cps_ir/type_propagation.dart
@@ -3020,7 +3020,21 @@ class TypePropagationVisitor implements Visitor {
 
   @override
   void visitForeignCode(ForeignCode node) {
+    bool firstArgumentIsNullable = false;
+    if (node.arguments.length > 0) {
+      AbstractConstantValue first = getValue(node.arguments.first.definition);
+      if (first.isNothing) {
+        setValue(node, nothing);
+        return;
+      }
+      firstArgumentIsNullable = first.isNullable;
+    }
     setValue(node, nonConstant(node.storedType));
+    node.isSafeForElimination =
+        !node.nativeBehavior.sideEffects.hasSideEffects() &&
+        (!node.nativeBehavior.throwBehavior.canThrow ||
+         (!firstArgumentIsNullable &&
+          node.nativeBehavior.throwBehavior.isOnlyNullNSMGuard));
   }
 
   @override