[proxy] Fix invalid call to getter in [[Get/Set/Has]]

Fixes the implementation of step 9 in the Proxy's internal [[Get]]
method:

Let targetDesc be ? target.[[GetOwnProperty]](P)

If P is an accessor, this should not result in a call to the getter.
Likewise in [[Set]] and [[Has]].

https://tc39.github.io/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-get-p-receiver

Bug: chromium:776338
Change-Id: I2652ffab2b3e4c38de00a82b8419192fdc768951
Reviewed-on: https://chromium-review.googlesource.com/732897
Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48825}

src/builtins/builtins-proxy-gen.cc

@@ -494,7 +494,7 @@ void ProxiesCodeStubAssembler::CheckGetSetTrapResult(
   Node* instance_type = LoadInstanceType(target);
   TryGetOwnProperty(context, target, target, map, instance_type, name,
                     &if_found_value, &var_value, &var_details, &var_raw_value,
-                    check_passed, &check_in_runtime);
+                    check_passed, &check_in_runtime, kReturnAccessorPair);
 
   BIND(&if_found_value);
   {
@@ -592,7 +592,7 @@ void ProxiesCodeStubAssembler::CheckHasTrapResult(Node* context, Node* target,
   Node* instance_type = LoadInstanceType(target);
   TryGetOwnProperty(context, target, target, target_map, instance_type, name,
                     &if_found_value, &var_value, &var_details, &var_raw_value,
-                    check_passed, if_bailout);
+                    check_passed, if_bailout, kReturnAccessorPair);
 
   // 9.b. If targetDesc is not undefined, then (see 9.b.i. below).
   BIND(&if_found_value);

src/code-stub-assembler.cc

@@ -6761,7 +6761,7 @@ void CodeStubAssembler::TryGetOwnProperty(
     Label* if_not_found, Label* if_bailout) {
   TryGetOwnProperty(context, receiver, object, map, instance_type, unique_name,
                     if_found_value, var_value, nullptr, nullptr, if_not_found,
-                    if_bailout);
+                    if_bailout, kCallJSGetter);
 }
 
 void CodeStubAssembler::TryGetOwnProperty(

src/code-stub-assembler.h

@@ -1486,7 +1486,7 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
                          Label* if_found, Variable* var_value,
                          Variable* var_details, Variable* var_raw_value,
                          Label* if_not_found, Label* if_bailout,
-                         GetOwnPropertyMode mode = kCallJSGetter);
+                         GetOwnPropertyMode mode);
 
   Node* GetProperty(Node* context, Node* receiver, Handle<Name> name) {
     return GetProperty(context, receiver, HeapConstant(name));

test/mjsunit/regress/regress-776338.js

@@ -0,0 +1,44 @@
+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+const obj = {};
+Object.defineProperty(obj, 'value', {
+  enumerable: true,
+  configurable: true,
+  get: assertUnreachable,
+  set: assertUnreachable,
+});
+
+let called_get = false;
+let called_has = false;
+let called_set = false;
+
+const has = function(target, prop) {
+  assertEquals('value', prop);
+  called_has = true;
+  return false;  // Need to return false to trigger GetOwnProperty call.
+};
+
+const get = function(target, prop) {
+  assertEquals('value', prop);
+  called_get = true;
+  return 'yep';
+};
+
+const set = function(target, prop, value) {
+  assertEquals('value', prop);
+  called_set = true;
+  return true;    // Need to return true to trigger GetOwnProperty call.
+};
+
+const proxy = new Proxy(obj, { has, get, set });
+
+assertFalse(Reflect.has(proxy, 'value'));
+assertTrue(called_has);
+
+assertEquals('nope', proxy.value = 'nope');
+assertTrue(called_set);
+
+assertEquals('yep', proxy.value);
+assertTrue(called_get);