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/compiler/access-builder.h b/src/compiler/access-builder.h
index 7d0bda1..d6385e4 100644
--- a/src/compiler/access-builder.h
+++ b/src/compiler/access-builder.h
@@ -34,12 +34,21 @@
   // Provides access to ExternalArray::external_pointer() field.
   static FieldAccess ForExternalArrayPointer();
 
+  // Provides access to Map::instance_type() field.
+  static FieldAccess ForMapInstanceType();
+
+  // Provides access to String::length() field.
+  static FieldAccess ForStringLength();
+
+  // Provides access to JSValue::value() field.
+  static FieldAccess ForValue();
+
+  // Provides access Context slots.
+  static FieldAccess ForContextSlot(size_t index);
+
   // Provides access to FixedArray elements.
   static ElementAccess ForFixedArrayElement();
 
-  // TODO(mstarzinger): Raw access only for testing, drop me.
-  static ElementAccess ForBackingStoreElement(MachineType rep);
-
   // Provides access to Fixed{type}TypedArray and External{type}Array elements.
   static ElementAccess ForTypedArrayElement(ExternalArrayType type,
                                             bool is_external);