Landing: Write protect executable pages in the VM.

runtime/vm/assembler_ia32.cc

Index: runtime/vm/assembler_ia32.cc
diff --git a/runtime/vm/assembler_ia32.cc b/runtime/vm/assembler_ia32.cc
index a84dc06358cb6874449b721214626407ffda829f..177dc091c2d9188fd59d244bf779cfde14c51b4c 100644
--- a/runtime/vm/assembler_ia32.cc
+++ b/runtime/vm/assembler_ia32.cc
@@ -80,6 +80,8 @@ class DirectCallRelocation : public AssemblerFixup {
     int32_t delta = region.start() + position + sizeof(int32_t);
     region.Store<int32_t>(position, pointer - delta);
   }
+
+  virtual bool IsPointerOffset() const { return false; }
 };