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/src/base/compiler-specific.h b/src/base/compiler-specific.h
index 475a32c..9755fc1 100644
--- a/src/base/compiler-specific.h
+++ b/src/base/compiler-specific.h
@@ -7,15 +7,13 @@
 
 #include "include/v8config.h"
 
-// Annotate a variable indicating it's ok if the variable is not used.
-// (Typically used to silence a compiler warning when the assignment
-// is important for some other reason.)
+// Annotate a typedef or function indicating it's ok if it's not used.
 // Use like:
-//   int x ALLOW_UNUSED = ...;
+//   typedef Foo Bar ALLOW_UNUSED_TYPE;
 #if V8_HAS_ATTRIBUTE_UNUSED
-#define ALLOW_UNUSED __attribute__((unused))
+#define ALLOW_UNUSED_TYPE __attribute__((unused))
 #else
-#define ALLOW_UNUSED
+#define ALLOW_UNUSED_TYPE
 #endif
 
 
@@ -39,8 +37,6 @@
 #define FINAL final
 #elif V8_HAS___FINAL
 #define FINAL __final
-#elif V8_HAS_SEALED
-#define FINAL sealed
 #else
 #define FINAL /* NOT SUPPORTED */
 #endif