Update to V8 with partial snapshots. This is taken from the partial_snapshot branch of V8.
diff --git a/src/x64/assembler-x64.h b/src/x64/assembler-x64.h
index 3f2aef0..64fbd88 100644
--- a/src/x64/assembler-x64.h
+++ b/src/x64/assembler-x64.h
@@ -113,8 +113,8 @@
     return code_ & 0x7;
   }
 
-  // (unfortunately we can't make this private in a struct when initializing
-  // by assignment.)
+  // Unfortunately we can't make this private in a struct when initializing
+  // by assignment.
   int code_;
 };