Enable GVN on HForeignNew

sdk/lib/_internal/js_runtime/lib/js_number.dart

Index: sdk/lib/_internal/js_runtime/lib/js_number.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/js_number.dart b/sdk/lib/_internal/js_runtime/lib/js_number.dart
index 1f9748c6bdb15b20b41ecac1ab116e11f5dde042..7513b1e93c539b29c8461979a508d5a6c3ef644e 100644
--- a/sdk/lib/_internal/js_runtime/lib/js_number.dart
+++ b/sdk/lib/_internal/js_runtime/lib/js_number.dart
@@ -56,7 +56,7 @@ class JSNumber extends Interceptor implements num {
     return JS('num', r'# % #', this, b);
   }
 
-  num abs() => JS('returns:num;effects:none;depends:none;throws:never',
+  num abs() => JS('returns:num;effects:none;depends:none;throws:never;gvn:true',
       r'Math.abs(#)', this);
 
   num get sign => this > 0 ? 1 : this < 0 ? -1 : this;