Merge V8 at 3.9.24.17

Bug: 5688872
Change-Id: I323fc8679f47b5f9e1539e9223c9da4b61a8947e
diff --git a/src/assembler.h b/src/assembler.h
index 918a2a6..f960b58 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -62,6 +62,10 @@
   Isolate* isolate() const { return isolate_; }
   int jit_cookie() { return jit_cookie_; }
 
+  // Overwrite a host NaN with a quiet target NaN.  Used by mksnapshot for
+  // cross-snapshotting.
+  static void QuietNaN(HeapObject* nan) { }
+
  private:
   Isolate* isolate_;
   int jit_cookie_;