Fix mozilla regress-398085-01 failure on windows.

src/x64/lithium-codegen-x64.h

Index: src/x64/lithium-codegen-x64.h
diff --git a/src/x64/lithium-codegen-x64.h b/src/x64/lithium-codegen-x64.h
index 4eab56c5b4b54789d67f74761fd89d56173cd3e1..4286d07de74114be174caf4133dab6626c184ab4 100644
--- a/src/x64/lithium-codegen-x64.h
+++ b/src/x64/lithium-codegen-x64.h
@@ -345,6 +345,13 @@ class LCodeGen BASE_EMBEDDED {
   void DoStoreKeyedExternalArray(LStoreKeyed* instr);
   void DoStoreKeyedFixedDoubleArray(LStoreKeyed* instr);
   void DoStoreKeyedFixedArray(LStoreKeyed* instr);
+#ifdef _MSC_VER
+  // On windows, you may not access the stack more than one page below
+  // the most recently mapped page. To make the allocated area randomly
+  // accessible, we write an arbitrary value to each page in range
+  // rsp + offset - page_size .. rsp in turn.
+  void MakeSureStackPagesMapped(int offset);
+#endif
 
   Zone* zone_;
   LPlatformChunk* const chunk_;