Migrated several tests from blink to V8 repository.

test/webkit/dfg-cfg-simplify-eliminate-set-local-type-check-then-branch-not-null-and-decrement.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions
 // are met:
 // 1.  Redistributions of source code must retain the above copyright
 //     notice, this list of conditions and the following disclaimer.
 // 2.  Redistributions in binary form must reproduce the above copyright
 //     notice, this list of conditions and the following disclaimer in the
 //     documentation and/or other materials provided with the distribution.
 //
 // THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
 // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 // DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 // DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 // (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 // LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 // ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 description(
-"Tests the behavior of Array.prototype.concat while the array is having a bad time due to one of the elements we are concatenating."
+"Tests what happens when CFG simplification leads to the elimination of a set local that had a type check, and then we branch on the variable not being null while decrementing the variable in the same basic block."
 );
 
-Object.defineProperty(Array.prototype, 0, { writable: false });
-shouldBe("[42].concat()", "[42]");
+function foo(o) {
+    var x;
+    if (o.f)
+        x = o.g;
+    else
+        x = o.h;
+    var y = x != null;
+    x--;
+    if (y)
+        return y;
+    else
+        return false;
+}
+
+for (var i = 0; i < 500; ++i) {
+    var o = {f:foo};
+    var expected;
+    if (i < 450) {
+        o.g = i;
+        expected = "true";
+    } else {
+        o.g = null;
+        expected = "false";
+    }
+    shouldBe("foo(o)", expected);
+}