Handle ES2015 Function.name in CallSite::GetMethodName

test/mjsunit/stack-traces-custom.js

 // Copyright 2015 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.
 
-var o = { f: function() { throw new Error(); } };
+var o = {
+  f: function() { throw new Error(); },
+  get j() { o.h(); },
+  set k(_) { o.j; },
+};
 o.g1 = function() { o.f() }
 o.g2 = o.g1;
 o.h = function() { o.g1() }
 
-Error.prepareStackTrace = function(e, frames) { return frames; }
-
 try {
-  o.h();
+  o.k = 42;
 } catch (e) {
+  Error.prepareStackTrace = function(e, frames) { return frames; };
   var frames = e.stack;
+  Error.prepareStackTrace = undefined;
   assertEquals("f", frames[0].getMethodName());
   assertEquals(null, frames[1].getMethodName());
   assertEquals("h", frames[2].getMethodName());
-  assertEquals(null, frames[3].getMethodName());
+  assertEquals("j", frames[3].getMethodName());
+  assertEquals("k", frames[4].getMethodName());
+  assertEquals(null, frames[5].getMethodName());
 }