Landing: Write protect executable pages in the VM.

runtime/vm/assembler_arm.h

Index: runtime/vm/assembler_arm.h
===================================================================
--- runtime/vm/assembler_arm.h	(revision 32487)
+++ runtime/vm/assembler_arm.h	(working copy)
@@ -293,6 +293,11 @@
   // Misc. functionality
   intptr_t CodeSize() const { return buffer_.Size(); }
   intptr_t prologue_offset() const { return prologue_offset_; }
+
+  // Count the fixups that produce a pointer offset, without processing
+  // the fixups.  On ARM there are no pointers in code.
+  intptr_t CountPointerOffsets() const { return 0; }
+
   const ZoneGrowableArray<intptr_t>& GetPointerOffsets() const {
     ASSERT(buffer_.pointer_offsets().length() == 0);  // No pointers in code.
     return buffer_.pointer_offsets();