Upgrade V8 to 5.1.281.57  DO NOT MERGE

FPIIM-449

Change-Id: Id981b686b4d587ac31697662eb98bb34be42ad90
(cherry picked from commit 3b9bc31999c9787eb726ecdbfd5796bfdec32a18)
diff --git a/test/mjsunit/es6/symbols.js b/test/mjsunit/es6/symbols.js
index 3833857..9bac41f 100644
--- a/test/mjsunit/es6/symbols.js
+++ b/test/mjsunit/es6/symbols.js
@@ -25,7 +25,7 @@
 // (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: --expose-gc --allow-natives-syntax --harmony-tostring
+// Flags: --expose-gc --allow-natives-syntax
 
 var symbols = []
 
@@ -86,6 +86,7 @@
 
 
 function TestConstructor() {
+  assertEquals(0, Symbol.length);
   assertSame(Function.prototype, Symbol.__proto__)
   assertFalse(Object === Symbol.prototype.constructor)
   assertFalse(Symbol === Object.prototype.constructor)