Update V8 to version 4.1.0.21

This is a cherry-pick of all commits up to and including the
4.1.0.21 cherry-pick in Chromium.

Original commit message:

Version 4.1.0.21 (cherry-pick)

Merged 206e9136bde0f2b5ae8cb77afbb1e7833e5bd412

Unlink pages from the space page list after evacuation.

BUG=430201
LOG=N
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/953813002

Cr-Commit-Position: refs/branch-heads/4.1@{#22}
Cr-Branched-From: 2e08d2a7aa9d65d269d8c57aba82eb38a8cb0a18-refs/heads/candidates@{#25353}

---

FPIIM-449

Change-Id: I8c23c7bbb70772b4858fe8a47b64fa97ee0d1f8c
diff --git a/test/mjsunit/array-natives-elements.js b/test/mjsunit/array-natives-elements.js
index d63346d..a19a931 100644
--- a/test/mjsunit/array-natives-elements.js
+++ b/test/mjsunit/array-natives-elements.js
@@ -274,14 +274,11 @@
   assertEquals([1,1,2,3], a4);
   a4 = [1,2,3];
   a4.unshift(1.1);
-  // TODO(verwaest): We'll want to support double unshifting as well.
-  // assertTrue(%HasFastDoubleElements(a4));
-  assertTrue(%HasFastObjectElements(a4));
+  assertTrue(%HasFastDoubleElements(a4));
   assertEquals([1.1,1,2,3], a4);
   a4 = [1.1,2,3];
   a4.unshift(1);
-  // assertTrue(%HasFastDoubleElements(a4));
-  assertTrue(%HasFastObjectElements(a4));
+  assertTrue(%HasFastDoubleElements(a4));
   assertEquals([1,1.1,2,3], a4);
   a4 = [{},2,3];
   a4.unshift(1);