[cleanup] Add missing test coverage for ObjectIsArrayBuffer operator.

The ObjectIsArrayBuffer simplified operator, which is used to implement
the ArrayBuffer.isView() builtin, didn't have any test coverage.

Bug: v8:8015
Change-Id: Ia15e35bc4ae61627137f7a89976560a8d3db771f
Reviewed-on: https://chromium-review.googlesource.com/1238215Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56112}

test/mjsunit/compiler/array-buffer-is-view.js

+// Copyright 2018 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.
+
+// Flags: --allow-natives-syntax --opt
+
+// Test that ObjectIsArrayBufferView lowering works correctly
+// in EffectControlLinearizer in the case that the input is
+// known to be a HeapObject by TurboFan. For this we use the
+// simple trick with an object literal whose field `x` will
+// only ever contain HeapObjects and so the representation
+// tracking is going to pick it up.
+(function() {
+  function foo(x) {
+    return ArrayBuffer.isView({x}.x);
+  }
+
+  assertFalse(foo(Symbol()));
+  assertFalse(foo("some string"));
+  assertFalse(foo(new Object()));
+  assertFalse(foo(new Array()));
+  assertFalse(foo(new ArrayBuffer(1)));
+  assertTrue(foo(new Int32Array(1)));
+  assertTrue(foo(new DataView(new ArrayBuffer(1))));
+  %OptimizeFunctionOnNextCall(foo);
+  assertFalse(foo(Symbol()));
+  assertFalse(foo("some string"));
+  assertFalse(foo(new Object()));
+  assertFalse(foo(new Array()));
+  assertFalse(foo(new ArrayBuffer(1)));
+  assertTrue(foo(new Int32Array(1)));
+  assertTrue(foo(new DataView(new ArrayBuffer(1))));
+  assertOptimized(foo);
+})();
+
+// Test that ObjectIsArrayBufferView lowering works correctly
+// in EffectControlLinearizer in the case that the input is
+// some arbitrary tagged value.
+(function() {
+  function foo(x) {
+    return ArrayBuffer.isView(x);
+  }
+
+  assertFalse(foo(1));
+  assertFalse(foo(1.1));
+  assertFalse(foo(Symbol()));
+  assertFalse(foo("some string"));
+  assertFalse(foo(new Object()));
+  assertFalse(foo(new Array()));
+  assertFalse(foo(new ArrayBuffer(1)));
+  assertTrue(foo(new Int32Array(1)));
+  assertTrue(foo(new DataView(new ArrayBuffer(1))));
+  %OptimizeFunctionOnNextCall(foo);
+  assertFalse(foo(1));
+  assertFalse(foo(1.1));
+  assertFalse(foo(Symbol()));
+  assertFalse(foo("some string"));
+  assertFalse(foo(new Object()));
+  assertFalse(foo(new Array()));
+  assertFalse(foo(new ArrayBuffer(1)));
+  assertTrue(foo(new Int32Array(1)));
+  assertTrue(foo(new DataView(new ArrayBuffer(1))));
+  assertOptimized(foo);
+})();