Remove grab-bag includes of v8.h from everywhere.

src/layout-descriptor.cc

Index: src/layout-descriptor.cc
diff --git a/src/layout-descriptor.cc b/src/layout-descriptor.cc
index b961a7de96dd7b88a02be10b25b9230141bfff9f..11a72e732dbb023fb2802d3c9d841bf7b57da8aa 100644
--- a/src/layout-descriptor.cc
+++ b/src/layout-descriptor.cc
@@ -2,12 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include <sstream>
+#include "src/layout-descriptor.h"
 
-#include "src/v8.h"
+#include <sstream>
 
 #include "src/base/bits.h"
-#include "src/layout-descriptor.h"
+#include "src/handles-inl.h"
 
 using v8::base::bits::CountTrailingZeros32;