Change LookupForWrite to always do a full lookup and check the result.

test/mjsunit/regress/readonly2.js

Index: test/mjsunit/regress/readonly2.js
diff --git a/test/mjsunit/regress/regress-2539.js b/test/mjsunit/regress/readonly2.js
similarity index 73%
copy from test/mjsunit/regress/regress-2539.js
copy to test/mjsunit/regress/readonly2.js
index 5d263f8912bb7f44083d159cfead81ba33a3a3b4..4e539250d55cd7656c70d2fa0bd8ef7a97527db0 100644
--- a/test/mjsunit/regress/regress-2539.js
+++ b/test/mjsunit/regress/readonly2.js
@@ -25,31 +25,38 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --allow-natives-syntax
+Object.defineProperty(this, "x", { writable:true });
 
-"use strict";
-var dispatcher = {};
-dispatcher.func = C;
-
-function A() {
-  B(10, 11);
+function s(v) {
+  v.x = 1;
 }
 
-function B(x,y) {
-  x = 0; y = 0;
-  dispatcher.func.apply(this, arguments);
-  assertSame(2, arguments.length);
-  assertSame(10, arguments[0]);
-  assertSame(11, arguments[1]);
+function s_strict(v) {
+  "use strict";
+  v.x = 1;
 }
 
-function C(x,y) {
-  assertSame(2, arguments.length);
-  assertSame(10, arguments[0]);
-  assertSame(11, arguments[1]);
+function c(p) {
+  return {__proto__: p};
 }
 
-A();
-A();
-%OptimizeFunctionOnNextCall(A);
-A();
+var o1 = c(this);
+var o2 = c(this);
+
+// Initialize the store IC.
+s(c(this));
+s(c(this));
+s_strict(c(this));
+s_strict(c(this));
+
+// Make x non-writable.
+Object.defineProperty(this, "x", { writable:false, value:5 });
+
+// Verify that direct setting fails.
+o1.x = 20;
+assertEquals(5, o1.x);
+
+// Verify that setting through the IC fails.
+s(o2);
+assertEquals(5, o2.x);
+assertThrows("s_strict(o2);", TypeError);